Tbf up to now the big third-parties surprised us by adding withdraw options at least relatively soon.
The financial giant will now allow customers to trade bitcoin, although they will not be able to withdraw it to self-custody.
…it should still be noted that trusted third-parties are security holes, and that the only true way to sovereignly use bitcoin is through the holding of one’s own private keys.
https://bitcoinmagazine.com/business/fidelity-has-opened-bitcoin-trading-to-the-public
Discussion
I would think they'd have to to be competitive.