Today many people have Bitcoin in their bank accounts from apps like Revolut, Vivid, etc. On exchanges like Binance, Coinbase, Kucoin, etc. In Apps like BlockFi, Nexo, etc.

But do they really have Bitcoins? No, and I explain why

First of all I must define the assets according to the type.

I will cite 3 examples:

FIAT (Dollars, euros, etc): A dollar is nothing more than money in the form of debt. A dollar per se is worth nothing, it is only worth because there is a state backed by an army and an education, etc. That forces its citizens to use their currency as currency of account, that is, you have to pay taxes and you have to agree to collect in that currency by law under duress. Without an armed force we would not have the obligation to use that money and therefore if it is not the best money, it would stop being used in front of others. The dollar, for example, is not bad money, since many countries become dollarized when the local currency dies, examples are Argentina, Venezuela, Cuba, etc.

Ultimately, the dollar depends on third parties, on a state that supports it and on a central bank that stabilizes its price by withdrawing money from the economy or injecting it through interest rates and other mechanisms.

FIAT money is debt, and a physical and digital asset.

Gold: Gold has a value that does not depend on a third party, nobody owes you anything. It is not debt. It is an asset called real, not debt. You do not need a third party to pay his debt, but there are third parties who want the gold, it has a decentralized value not imposed by a central body.

Gold ETF: A gold ETF is nothing more than an investment fund that owns gold and in which you can invest. In this case, you have an asset that behaves in its value the same as gold, but you do not have gold, you have shares of a fund that replicates the value of gold. In other words, what you have is the ownership of a debt. If the company that created the ETF goes bankrupt, you lose your "gold", that is, you did not have gold, but debt. It is also a digital asset.

The same happens with Bitcoin, if you have Bitcoin in your own wallet such as Wasabi, Electrum, etc. You have Bitcoin, you control it, you can spend it whenever you want. It is a real and digital asset. It has value on its own without depending on third parties.

But at the moment when you have Bitcoin in a third party such as Binance, Coinbase, etc. What you have is a financial asset that replicates the value of Bitcoin, you own a debt and depend on a third party.

This is not to say that it is not useful to have Bitcoin on centralized sites, for trading for example. But Bitcoin was invented to be money without intermediaries and in an environment of uncertainty, bankruptcies, inflation, brutal tax increases, etc. It would be wise to have real assets and not debt. Be it gold, Bitcoin or whatever.