> .com is basically seen as just a mysterious string that ends URLs in much the same way that "http" begins URLs.

This is 100% true. And yet, for the average person, it's viewed as the default mysterious string that ends a website's "name". Anything else is viewed as slightly questionable, although most people are aware of .org and .net as sometimes legitimate exceptions. I think most people would be less likely to enter their credit card information on a ".biz" domain, even though they couldn't express any accurate reason why that made it less trustworthy. That's significant, even if it makes no technological difference.