Apple Pay on web is fantastic. I don't use an iPhone, but specifically use my iPad for online purchases from any retailer that supports Apple Pay.

I don't think I've seen it either. What I have seen are requests for my App Store password on occasion when I launch, say, Google Maps. It's infuriating because when I'm out in the world, I don't have access to my passwords and I don't remember them.

It's a sign in to Apple, if not a sign in with Apple, and it's weird because what I'm trying to use is Google's Maps application without signing into anything. What is going on with all of this?

I think that the point of using Sign In w/ Apple is to prevent you from having to remember more than one password. It is only used when you would have to create/remember a password anyway so it won’t get in your way when you are out an about any more than signing in with Google/Facebook or your own email/password.