I only know of one or two racers who wear Dainese (although one of him is slightly popular ) while I see a TON of racers in not just GP but AMA and WSBK wearing Spidi.
Of course, there's also a few racers who wear Joe Rocket, and MotoGP who I've heard have somewhat shabby quality (although I hear that JR has come a long way, and I heard MotoGP was shabby from only a few ppl).