Dan -
I don`t know a single person alive who can`t "hit" a high G. I know many who can`t play one, but "hitting" a note is much different then "playing" a note.
However, your point is valid. Generally, lead players have at least a solid G range. That means they can open up a show with a lick up to a high G and close that same show on a high G, then do another one later that day. I have met a few lead players who have say, high A to CC ranges, but not dependably, meaning, they can`t depend on having that CC there at the end of a performance.
Listen through some of the major jazz/latin recordings and count the times the actual lead player has to go above a G. When I say actual lead player, I don`t mean, say, a recording of Gordon Goodwin`s Big Phat Band with Arturo Sandoval and Wayne Bergeron playing. Obviously, there is going to be some really high stuff in that piece BECAUSE they have the players there that can do it.
There aren`t too many pieces out there that demand more then a high G range. Yeah, they`re there, but for the average professional jazz ensemble, the chances of having above a high G required more then once or twice in a show is slim. That doesn`t mean you won`t hear a lead player go above it, just that the piece doesn`t require it. I don`t know what groups you`ve played with, but I`ve played with enough to know that lead players often go higher then whats written, A, because it /is/ fun, and the crowd loves it, and B, because they can
.
Don`t get yourselves in rutts because you can`t play a high G all the time. I`m auditioning for Eastman, Juilliard, Manhattan, and Northwestern this spring (to name a few), and I only have a playable high E range. There again, meaning, I can play an E at the beginning and end of a show. Does that mean I can`t manage a high G in the middle of Kiss Me Kate or The Producers? No, it just means I wouldn`t want to perform a solo requiring it (yet.)
Practice, envision, listen and you`ll do well. Just don`t THINK to much!
Cheers!
Aaron