Whitepapers are known for being the defining document in a crypto projects success.
Per Investopedia: A white paper, also written as "whitepaper", is an informational document usually issued by a company or not-for-profit organization to promote or highlight the features of a solution, product, or service that it offers or plans to offer. White papers are also used as a method of presenting government policies and legislation and gauging public reaction.
Now with this being said it does not specify this to the Cryptocurrency/Blockchain industry as a whole. If you are a crypto enthusiast or just a investor trying to make a quick buck a whitepaper is always the first thing you look at when checking the validity of the project. The mantra is that without a proper "White Paper" the project is more likely to be flagellant or a "scam". A lot of the same people that strongly believe in this notion wont accept anything less then a 25 page document about the project. Which in regards to the concept of asset management isn't inherently a bad thing.
This vision of "Whitepaper or Bust" is kind of moronic. See based on the basic understanding of what a whitepaper is; a "technical document", a 'White Paper' could be just about anything. When working on IP we referred to our documents as Teaching Documents, these documents where used in part to create a Non-Provisional patent application "Each non-provisional patent application should contain a title, a background of the invention, a summary of the invention, a detailed description of the invention, one or more claims, and drawings"
A Business Plan, A patent Application, Any form of technical document in relation to the operation of something could in essence be considered a "white paper". Im going to be using business planning and patent applications as my prime examples here.
With the conception of a patent or invention there are a few boxes we like to check. What is the current day problem and what are its impact's, What is the proposed solution. How does the proposed solution work in comparison to todays solution, What are the new and not obvious features?
For example adding a leg to the back of the chair so you could lean back wouldn't be considered new and not obvious, however adding a gyroscope and some for of counterbalance system allowing you to lean back and not fall would be. Now in this example there will be a-lot as to how this could work.
The approach is the same in a business plan, you spell out the solution you are trying to build and how to make it profitable. Ex: What products and services are offered, how is it unique then what's rudimentary available and does it serve a purpose for customers, what are the financial needs and what/when a profit be seen?
The difference in the above example is one thing, the audience. When figuring out the type of document needed you need to ask yourself one question, who is my audience?
So, are white papers needed?
In my opinion I would say it would be dependent on the industry, use case, and structure of the project.
Is the project building its own blockchain outside of BSC, ETH, POLY, or other large blockchain's. Projects building their own blockchain solution/node system with varying principles, a good example of this is the transaction fee difference on BSC and ETH. With systems like this because of the scale and the underlaying use-case a White Paper would be necessary. If your system or project is just accepting crypto currency you wouldn't need a white paper.
A real time example here would be Brank.io
Brank.io is a simulated trading platform. A paper trading platform that allows you to easily track wins an loses. For free, They also have tournaments where you can pay to play, if you out trade a majority of the people (depending on seat size) you'll win. The model for brank is very simple, they offer a free tool for everyone, and free tournaments. They also offer paid services like tournaments for prizes, access to live trading tips and tricks like how to read charts better, how to strategize your portfolio, risk mitigation, different things to help you be a better trader. Brank ran into a issue, a payment processing system. Brank needed a way to streamline the process's from a business perspective, how to get tournaments rolling. Originally they offered a on platform token with a reward pool tied too it, but it was done through a third party payment system. One way around all this was cryptocurrency. Instead of Brank just accepting another currency on the market, they decided to build their own on the BSC network.
Now that Brank has their own cryptocurrency would they need a White Paper spelling out the use of the token they built? My answer would be no, for a few reasons. The main and most important reason was WHY did they do go to crypto? They did it to further the reach of their platform, tailor it more for the wanted audience. The platform wasn't designed around their token, their token wasn't made to fund the building of the platform neither. In instances like this its all about the perspective the entity is coming from and headed.
In Brank's case, instead of having a PDF white paper, they have a roadmap for where and what the business is doing in regards to the platform, They have a formal page informing Users of the token, its properties, and its use case (gain access to Brank's service's). 
So currently Brank is sitting around $0.053 USD, the entry price is about $5.30.
If we go to the current leader board it shows what it means to win.
As you see first place is winning $21.41147 or 403.990 BRANK token.
Say the price of the Token shoots up to $0.10 before the tournament ended the winnings in USD would change to $40.
Based on how Brank is using its token, It doesn't warrant a "white Paper" due to the use case being very obvious in this instance and was usable the moment the Token launched.
When it comes down to distinguishing if a project needs all kinds of technical documents that in some instances may be redundant and not even necessary. Remember to ask yourself a few things when looking at projects and their technical documents. What is it used for, How does the Entity benefit from you using the token, How practical is the use or utility of the token(is it another "NFT marketplace", a "PLAY - 2 - EARN" nft game that makes your really spend money to get a NFT that doesn't have the value you paid for, a token that's meant to re distribute wealth by taxing every transaction into dust by burning a small portion of a 1 quadrillion supply)
Remember to do your own research and remember things don't have to be complicated to be successful.