It seems far too often the goalkeeper lets in a free kick because he has to properly react only when the ball is past the wall. Without a wall, he can watch the ball right from the kick.
Perhaps a wall was a good idea at first, but now the football world has more experience of placing free kicks and getting it past a wall, especially with certain players, surely it's better to let the keeper see it all the way. The vast, vast majority of goals are scored in the penalty area, the vast, vast majority of distant shots balloon over the goal or are hit right at the keeper. The vast majority of long-range shots on target are saved. I also think the vast majority of long-range goals happen thanks to the power of surprise and unexpected flair, rather than preparation and knowing where the shot is coming from and when.
While a few free kicks hit the wall, would more be saved if there was no wall?
Especially for the ones even further away than the edge of the penalty area, that still for some reason has a wall setup. If the guy's going to shoot from all the way over there, the keeper would have no trouble stopping it unless it's beyond his reach somehow.