"Systems like this are usually a bit too easy to game. That is, once a player figures out how to increase the stat they want through the least amount of effort, they'll do it.
It can also keep you from changing up the way you play easily. We want to allow some amount of freedom in changing up how you play a single character. If I've played my Wizard as a long-range glass cannon the entire game, and then get an amazing end-all item drop that makes me want to switch it up and go as more vitality-heavy battle style Wizard, I'd probably have to reroll. Whereas with our current systems it's just a matter of building up an item base that supports it.
In addition to all that, it isn't a system which is very user friendly. It's somewhat difficult to explain to the player exactly how those systems work. Not too many people are going to go through the entire game not caring and just playing how they want to play, they want to know exactly how to raise the stats they want, and it would be difficult to display or show how you're progressing outside of getting a point added. Then you're wondering "how exactly did that point get there and what do I need to do to get another one?"
Not everyone is into strict min-maxing, but almost everyone wants to know how to make a powerful character.
I think keeping some systems nebulous and somewhat unexplained to the player is fine, but something such as stat points, a core progression and "power" system, it should be as straight forward as possible. Especially where fast paced action - not toiling over hidden math and requirements - is the game.
With auto-stats you lose a small amount of customization, true, but gain a lot of freedoms in adding more - and more interesting - customization through other means.
Worm Cans Initialized."