They’re the only mega bank with both a 2% cash back card and a competitive HYSA
But even if it was $100k savings, you can get ~5% APY at BoA high yield savings through Merrill anyways. I don't recommend that since Fidelity works better for that type of account, but you could do it.
Other brokerages do the same sorts of things, Fidelity isn't alone in this. Schwab went a different way and decided to just buy a bank. Instead of like the BOA/Chase versions, where they bought a brokerage.