If a person feels that they need an extra character/account to serve as a mule to store goods beyond:
What they can carry on themselves
What they can carry in retainers
What they can store in their house (pending I expect..)
What they can store in their mailboxes (also pending I expect...)

Then perhaps they are playing the game in a manner that the developers did not intend? If that is the case, then I would understand the developers from trying to limit this form of gameplay if they feel it does not lead to a good overall experience.

I know, if I had easy infinite storage, I may never sell anything ever and hoard everything I ever got. This could have undesirable effects for the rest of the game/economy/interaction. (I am less likely to sell. Also, less likely to buy 'that newbie gear I sold 6 months ago to make space').

I have not played the game enough to say for certain, but is it really difficult to play the game in a reasonable manner given the amount of storage that SE is willing to give/sell us without the need to have an additional account?