This is one point about the OP's topic.

There are a lot of Shimano bikes out there.

SRAM or Campagnolo bikes are much rarer. So, I could imagine the temptation to get a bare frame to build up with Campy or SRAM components. Also details like choosing one's favorite crank length, chainrings, and cassette. And, of course, wheels.

There is, however, a thriving used market for "new pulls" if one gets a bike that is close.

Trek has their "Project One", build as you like it program. I haven't been very interested in that, but it is worth looking at the options available. Hmmm, it looks like Project One is only CF, no Campagnolo, and very expensive.