So long as you’re running Zwift under Windows, Zwift is using Internet Explorer regardless of whether you personally prefer to use other web browsers.
The issue with Internet Explorer is that when a user or security software changes security level settings or change the way Internet Explorer handles cache and cookies, it can prevent other apps from accessing Internet Explorer’s saved passwords feature. Sure, getting people to change their security settings back is just as applicable, but trying to instruct people on how to do that is an entirely different story. Resetting is much easier process involving far fewer steps.
Besides, people shouldn’t solely be trusting their web browsers to store important login information and account credentials. If active logins are lost and members don’t remember their passwords, that’s kinda their bad.