It says that they make reasonable inferences based on prior experience. It's just an email address, sure, but one associated with a service designed for "people not smart enough to be on the real Internet". For a long time, AOL didn't have Internet access at all, just keywords that took you to an internally hosted web page-like media view. It was generally understood that no one clever enough to grok the Internet would ever settle for constricting AOL access, so its usage came to connote cluelessness. By the time it opened up to the rest of the web, there were many viable local and national competitors.
OK, you're one of the handful of AOL users who picked it for non-clueless reasons. You can't be surprised that the rest of the world sees you as a tiny minority, though, and automatically assumes that @aol.com implies @i-dont-know-what-an-isp-is.net. I don't begrudge you your right to dig in your heels and resist. Hey, I had an Amiga for years after they stopped being cool - I get it! Shine on, crazy contrarian diamond! Your address may very well eventually come around to be hipster-cool and retro, and if so, congratulations! But if it doesn't, well, understand that you made the decision.
FWIW, Gmail's "Mail Fetcher" can be configured to pull mail out of non-Google accounts and into a Gmail inbox. You could start using Gmail today and not miss a single @aol.com email, then gradually transition over a period of days/weeks/years as the legacy email slows to a trickle. I don't personally use Gmail and I'm not trying to push you onto it. I just wanted to point out that you don't have to pick a flag day to switch from one email provider to another. If you decide to transition, it can be as quick or gradual as you feel like that day.