The main reason for three-betting with many of the hands that you play out of the small blind against a button raise (when no one else is in) is defensive. That is you prefer to get the big blind out and play heads-up.


Now that you have successfully done this it makes sense to almost always auto-bet the flop. That's because if your opponent doesn't flop anything, which will be the case the majority of the time, it will be very difficult for him to call. This is especially true if you catch him with a weak raising hand.


I do agree that what you describe is a weakness of this play. However, given that there are seven bets now in the pot your opponent doesn't have to fold to frequently for your bet to be correct, and sometimes he may fold a hand that is better than yours.