Fair enough. I was listing common buffer size macros off the top of my head. But that's beside the point. The others, and many more, are meaningful. Programming, like life, is full of arbitrary limits, and programming as if you'll ever need to meaningfully store a 1MB path name often leads to needless complexity, and complexity breeds bugs.
But let people continue to use strcpy, and let the exploits continue to roll in. Fortunately they've slowed down over the years, thanks to alternatives like snprintf and people copy+pasting strlcpy, and not so much because people are passing glib string objects to library routines.