Not To Be Obtuse
. . . or anything . . .
The lock is abhorrent for two primary reasons:
1) It is often seen as lawyers solving a problem that didn't exist so as to avoid blame for accidents
("Well, we GAVE you a lock; all you had to do was USE it!), hence the "lawyer lock" epithet.
2) It adds another point of failure; a lock that malfunctions is more likely to cause a Failure To Fire and render the gun inoperable than it is to permit unwanted firing when it fails.
3) Oh, one other thing, it's seen as a blemish, an unnecessary interruption of the otherwise clean lines of a fine piece of machinery.
The supposed convenience (obviating the external trigger lock) is overshadowed by the discomforting fact that this lock is -- unlike an external device -- always present, since it's part of the gun, meaning that -- unlike the external device -- you can't leave the lock and key at home. You must now carry the key to the gun lock at all times when carrying said gun because, should the lock ever engage unbidden, the absence of the key awards you a pistol-shaped paperweight.
Actually, shouldn't we have seat belt locks? I mean, what if little Johnny disconnects his seat belt while riding in the back seat. Suddenly, he's at risk (remember, you're going to have an accident) and you can't reach him to fasten it. But wait! Our legal team has the answer! An integrated seat belt lock to prevent unwanted and unexpected opening of the belt.
Gawd, we are
SO brilliant.