Nobody has to take your BTC to benefit from it. All they have to do is eliminate you. If you've done a good job of hiding your keys, then they have just increased the value of their share of BTC.
What seems to be happening is that fiat is continuing to move commerce while crypto is powering the back end of transactions like Visa is doing. On the face of things, they're dealing in fiat. But what they're actually transferring is USDC.
In terms of BTC ETFs, the customer sees shares of the fund which has BTC on the back end.
Crypto solves many of the problems of finance for banks and institutions just as well as it solves them for the rest of us. They just have a harder time turning their ship around.