"Some people might use them as alts for inventory space" how does this effect you?
"Some people won't be attached to all of their characters" how does this effect you?
"Some people might use 7 slots as mule accounts" how does this effect you?
"Some people might reroll and give all their gear to their new character" how does this effect you?

The only thing that could possible effect you is people making alt's to troll and this can be solved without the hassle of preventing people from enjoying the game how they want to - an option for blacklisting all characters from that account. You don't need to come up with these grandiose ideas that penalize everyone just because "some people might" instead come up with real solutions to problems. Heck, for you "inventory" argument you could just make it so that you can't mail things to your other characters (but I don't agree with that either, but it's a better alternative than "NO ONE CAN HAVE FREE ALTS")
In regards to every other point you made - it doesn't effect you, so don't complain about it.