It's more of a testing limitation. These programs are only occasionally tested against humans. You need expert players to test, they're not available all the time, and it takes a long time to play a single game (unlike poker). You can use databases of online games but it won't tell you how the player would have responded to a different move 37.
If you're writing a program to beat anyone, there isn't much point in optimizing the algorithm for a specific opponent's weaknesses when there are improvements to make that would work against anyone and the improvement in strength can be evaluated using computer testing alone.
Work on exploiting specific opponents' weaknesses is typically done using much simpler games (check out what's been done for rock paper scissors).
If you're writing a program to beat anyone, there isn't much point in optimizing the algorithm for a specific opponent's weaknesses when there are improvements to make that would work against anyone and the improvement in strength can be evaluated using computer testing alone.
Work on exploiting specific opponents' weaknesses is typically done using much simpler games (check out what's been done for rock paper scissors).