The have a lot more problems to deal with if they have to deal with all the people that include a stray space in the address. There are regexes out there that

The have a lot more problems to deal with if they have to deal with all the people that include a stray space in the address. There are regexes out there that catch all valid addresses that people reasonably use (including those with dashes and ending in .us) and the fact that all kinds of incompetent developers use a homebrewn regex is no reason to lower the best case scenario to "just don't validate". Just do it right.