But people who know and use the words foo and bar are almost exclusively developers, so they should know better eveb when typing a fake address to a random form. But it’s easy to type reflexively, without thinking, so I’m not surprised people do it.
Check out the MX record for meowcats.fun, for example. It points to suremail.info, which points to mailinator. I have never had that domain rejected by a form.
Shhh, don't tell anyone ;)