Glock wanted a self-named cartridge, just like .40 S&W and .357 SIG.
In addition, the .45 GAP is a silly answer to the problem that has been expressed about the 10mm frame size Glock, which is that it is too big, too fat and has no ergonomics.
So, instead of building an ergonomic .45 ACP duty pistol, for which consumers have been begging for over 20 years now, we get the GAP in a G22 frame with a G20 slide attached.
What they should have built instead is a duty size version of the G36 - taller to hold 8, 9 or 10 rounds in a single stack mag with a longer slide and barrel.
By the way, there are very few people who can really grip the G20/21 properly, with the forearm straight in line behind the grip. Fortunately for Glock, most of the "ninja" crowd usually boast (while beating their chests) that the G20/21 platform is comfortable for fear that if they tell the truth someone will pre-judge their other perceived "inadequacies."
I for one cannot properly grip a G20/21, and I am not ashamed to admit it. The reason is not because I am not a man. The reason is because the pistol is poorly designed with crappy ergonomics.
The boys over at Glock are kidding themselves if they think the SF (short frame reach version) really solves the problem, because it does not. It is "not enough."
What we didn't need was the GAP. What we did need was a comfortable Glock in .45 ACP, even if it was simply an 8, 9 or 10 round capacity pistol, something that must give the designers over at Glock a great deal of heartburn.