buying and holding bitcoins requires a specific knowledge that an "average joe" has difficulty to understand. For what I have seen, even a person with more experience or informatic culture must spend some time before being able to mastering this argument.
The "average joe" you are talking about, if he can't buy and store bitcoin because it's too hard for him, he probably doesn't know the difference between spot ETF and CFD either. So he is already in bitcoin using plus500 or any other regular broker. Exante for instance (fully regulated broker that I use to invest in stocks/bonds) have 150 krypto CFD trading pairs. On BTC/USD trading pair there is currenty 1$ spread
Most people do not invest, you need to remember that when you are investing, most people either don't or can't invest. I have seen a lot of people around me who never invested ever, they just live paycheck to paycheck either because they are idiots who spend any extra money they get, or they are just not doing a good job and not making enough money at all.
This is why I keep insisting on living at a level where it would make a profit when the time comes. I hope that people could end up with a good return, and they would invest their profits into something that makes them even more money, but billions around the world do not invest at all, and have no savings. Only some people do, and when you have like 500 million to 1 billion people investing that looks a lot, but we have 8 billion people, you need to remember that.