Internet Explorer - Why does Xbox Live sign-in prompt an IE pop-up?

I do not use Internet Explorer for web browsing, haven’t used it for years. I didn’t even know it was around anymore as I thought support for it went away long ago. Plus, Win10 uses Microsoft Edge for web browser by default. It is definitely not my default web browser, I can say with certainty; and I didn’t even know it was installed on my PC, to be honest.

So, why, then, do I get a pop-up box asking me if I want Internet Explorer to remember my password as I sign into “Xbox Live” from AoE2:DE?

Seems like a vulnerability / security risk, as Windows Security (Windows Defender?) isn’t set up for it, and maybe not my 3rd party anti-virus software either. Time to try to uninstall it, sure… but who knows if that will break the AoE2:DE login somehow.

Either way, why is it connecting to Internet Explorer here rather than MS Edge or the 3rd party (popular) browser I use by default?

I’ve noticed it before, but just never thought too much about it; and didn’t want to spend time posting about it here before.