I'm a totally separate person, and I can also verify that forcing business users to use IE for certain services is definitely a thing.

I'm not sure what your point is? It's not necessarily going to apply to ALL banks, but it'll probably apply to SOME of them, and that will suck if it happens to be your/my bank.

I used to work at a credit union in IT. I can confirm financial institution laziness knows no bounds. Separate from their laziness is the vendor compatibility. I can't count how many vendors do not update their software to run on modern browsers and relied on specific IE instances. Adding to all that is just the institution itself having decades old hardware and software because modernizing things can be incredibly expensive. The core my company used was incredibly outdated Unix and required a ton of different middleware just to make sure we were compliant where absolutely necessary. If it wasn't necessary nothing got done. And that's better than a lot of banks that could be running on some COBOL based core. Completely redoing the core will affect every middleware crap solution they've patchworked together to keep running over the past few decades and will be insanely resource, cost, and time intensive.

Even these days at my current company I run into this shit. Huntington bank requiring IE for check processing, or SAGE DB software requiring 2013 Access or else it won't work. These are huge companies still utilizing outdated piles of garbage.

oh, I also want to point out that you completely ignored my question; you said "There would have to be very significant reasons" and I asked what that was, and instead of responding with a clarification on what is required as a reason for a bank to actually do the thing, you attacked my position asking for more clarity on which banks were actually doing this, I'm sure in an effort to minimize the scale at which my experience is relevant, yet other lemmings have already chimed in to say that they have also witnessed the same lazy behavior.

Classic misdirection. So, what justification is required for banks to actually innovate? The only thing I've seen from banks is them trying everything they can not to; so I'm genuinely curious what justification is required to actually make a bank do something.

Please list all these banks near you that require IE?

yes.