That is fine in theory, but people in the original did this thing called muling which, when done by a lot of people at once, causes unnecessary stress on the server. The shared stash tab doesn’t replace muling, but reduces the impact it has on the server, because instead of creating a game with one character, dropping the item on the ground, leaving the game and joining with another character, you just stash whatever you found that you think needs to be muled, and then later on you may log with one of your mule toons and do all of your item transferring with a single connection.
In fact, in my opinion, if it was possible to have more tabs (say, 10 or more), you could keep most of your important stuff there and make way less mule characters