It's one thing that always puzzles me: when the software is distributed in binary form vendors sometimes provide several binaries compiled with a different versions of GCC. I use Opera browser as an example but I remember other software vendors do the same.
Opera provides several builds for their browser (http://snapshot.opera.com/unix/10.0-Alpha-1/intel-linux/):
Why is the GCC version stated? I suppose it has nothing to do with dependency management unlike the packaging (RPM or DEB) or Qt version.