If I close it, my credit score is negatively impacted by losing a decades old credit line. I don't particularly care about my credit score, and this sort of lock-in is pretty low friction, but changing banks can have costs.
I hate them, over the years that I banked with them, they have consistently been a bad bank. I think I have at least two complaints that went to the CFPB with them (both ended in my favor). I switched my banking activity to another institution years ago, but I do still have accounts open with them.
I'm a financially saavy rich white dude with a degree, and I still find it hard to sever the relationship. Imagine how lesser advantaged people feel. If you're choice is between WF and BOA because of geography or whatever, and you're used to financial institutions being shitty, why bother switching from one predatory institution to another?