One word: competition
The Walther 99 is a better gun in most respects than the Glock in 9mm. Better trigger, better sights, more ergonomic. The HK USP .45, for all its flaws, is usually a better, more comfortable shooter than the Glock 21, and the Sig 220 is really a better gun than either. The Glock 35 (and maybe 26/27) seem to be the only Glocks remaining at the head of their class.
Time for Glock to improve the grip and trigger. I won't buy any more Glocks till they do so.