the reason you can't send things to alts isn't a purposeful thing, it was a result of two things that they just decided to roll with because it's simply not relevant to the majority of players:
1) You can only send mail to people on your friends list, as a means to avoid RMT spam clogging the mail system.
2) You can't make friend requests to offline players, to avoid the same thing as #1 as well as just general abuse.

They could change it, but there's just simply not that much incentive on their end to do so.