It takes away the tedium of spamming attack over and over. It's not like it takes any thought, so I don't see any point in it... The time it frees up could be put to much better use via strategic elements that could be added, which the game definitely needs more of... With things like the use of abilities, tactics, or whatever else they might add.

Of course, even if they don't add those strategic elements, auto-attack would still be welcome, because chatting is still a lot better than button mashing mindlessly.