It's not so much that they don't understand, but rather that they don't care. People can buy Bitcoin for fun or to try to make money without believing in the ideology that was originally used to justify it.
There's literally nothing special about bitcoin, apart from its decentralised nature.
Other than that, it's just a big ledger. No different from virtually any other database. It's special because it's decentralised.
The way people use bitcoin however, completely reverses that and is extremely geared towards use of centralised parties. It's as if we built solar panels to generate electricity with which we heat up our oceans, causing ice caps to melt and global warming to occur. It's a bit of a joke.
We're now all valuing a system, above other systems, for its unique decentralised properties, while subsequently throwing that out the window, yet still expecting this system to be uniquely valuable. We're all introducing trust into a trustless system, and paying intermediaries and middlemen a cut in the process.
That's fine for other investments, e.g. productive assets that are valuable for other reasons. But it's not fine for an investment into something that's valuable because it's trustless, decentralised and disintermediating.
There's some nuance I'm leaving out of course, you can argue against this post, but by and large you can't ignore this massive disconnect between bitcoin's value proposition and bitcoin's reality. Nor can you argue anymore, like we used to, that it's just a phase. If anything, there's less and less regard for personally run wallets, personal nodes, personal mining, personal transactions, and an increase in use of centralised parties, with centralised wallet providers, cloud and company mining, transaction processors etc.
Then the whole angle of "trusted" is complex due to the parties that you are entrusting and the number of issues that they have suffered.
So then you look at banks and say ok, interesting, perhaps I haven't quite noticed the seamless ease of use layer that they provide, that I have undervalued simply because it's been a fact of life for so long it becomes invisible until you deal with the exact opposite.