In Vaudeville through the 50s, I would agree. But by the time the late-70s rolled around, we had Steve Martin, Robin Williams, and Richard Pryor running the stand-up world. Loud, fast, and brash. That was what sold tickets, that was what worked on television and that was the future of stand-up.
Until it wasn’t.
Richard Belzer, Gary Shandling, and Jerry Seinfeld were the only observational stand-ups that I can recall in the early-80s. (Love Stephen Wright, but he was more a dead-pan schtick.)
Jerry, though, made observational blossom. Others picked up and modified it. People like Denis Leary and Sam Kinison made observational comedy abrasive and dangerous. Ray Romano took it toward an examination of family. Jeff Foxworthy examines redneck culture.
Yes, Jerry owes a lot to the guys working the clubs in the Catskills, but modern observational comics owe a lot to Seinfeld.