I'm not sure that they don't try - it has been a few years since I stepped into a GC store. (Recent big box purchases have come from Sweetwater.)There was a time, long ago, that GC actually catered to pro-level local players. They don't even try anymore.
The last time I was at GC I found an Ibanez 6-string bass that I was interested in, enough to wheel and deal (and play hardball) for it. By the time the dust settled, I got the bass for effectively 27% of MSRP. (Then I turned around and put $900 worth of parts into it, so it is now a world-class 6-string bass. Its tone now resembles the low notes of a Steinway grand piano.