Does anybody have an answer for why the Ambassador Class never saw anywhere near as much use as the Excelsior and Galaxy Classes? Or any other class, for that matter...
From what I understand, the original model itself was built rather, shall we say, economically, and in a hurry for 'Yesterday's Enterprise,' which is why it lacked the complex curves of the original design. It was 'refit' for the modern era and made several more appearances on TNG.
According to Doug Drexler, the model was later evaluated for refit and reuse in the final scene of 'Generations' as one of the ships rescuing the survivors from the
Enterprise-D crash. (This was of course after it had appeared as the
Yamaguchi in the DS9 pilot.) It was apparently found to need too much work to be usable, and so was excluded.
Presumably, the studio didn't want to pay for the 'fixing' necessary to bring the model up to snuff for the model-based fleet work on DS9 either, and soon after the operations switched almost exclusively to CGI. As there had been no previous reason to build a CGI model of the ship, one did not exist and it therefore did not appear. A shame, really.
In-universe, the
U.S.S. Ambassador was said to have been launched circa 2315, so by the war it would have been a sixty year old design. (The TNG technical manual refers to it and the
Oberth as 'aging classes.') When coupled with the fact that we saw relatively few of them to start with, it's my theory that the class was in fact a literal pathfinder for the
Galaxy project - big and ambitious, perhaps too much, too fast.
It's possible that it wasn't a total success, but served technologically to pave the way for the
Galaxy. I tend to think that very few were built, perhaps a dozen to eighteen, with Starfleet opting instead by the time of the Dominion War for the newer, perhaps more successful
Galaxy and
Nebula classes, which would presumably fulfill the same roles.
Excelsiors and
Mirandas which we saw tons of presumably fulfilled different roles in the fleet.