Is it possible that the computer is trying to bunt or hit & run all the time INSTEAD of stealing? I can't think of any other reason why you shouldn't have a ton of SB attempts.
I agree with miller.randall though... My guys were getting thrown out way too often on "aggressive"... Now I set it on "normal", with my best base stealers set on "steal more", and it works out fine. (Sadly, I'm going against Pudge Rodriguez tonight... So my entire team is set on "don't steal"
...But tomorrow we'll be off and running again!)