Although, even bicycles (at least those designed for racing) are starting to become more and more proprietary. Try mixing and matching Shimano and Campagnolo shifters and derailleurs or using a seatpost from an aerodynamic frame in another one.
As for the seat post, it's these molded carbon frames that seem to be built for short use and then the trash that are problematic in my eyes. They're just wasteful and most of the people buying them are doing it just to buy some time for their various races.
Having gotten in to triathlons a bit lately, I'm constantly annoyed that someone can literally buy gear to make themselves minutes faster, even though our engines may be comparable. I wish the organizing bodies would standardize the equipment for competition.
That said, people who come into triathlon from a running background do tend to do better than swimmers or cyclists who have to learn the other two events.
Drivelines are more integrated now, with derailleurs, cog tooth profiles, chains, and shifters designed as a system with minimal thought given to cross compatibility. At best you could use a non-Campy/non-Shimano chain.
My understanding is that they aren't, at least where we are talking about indexed shifting (which is pretty much everything these days). The amount of cable pull per "click" is different between SRAM and Shimano, which means you can't use a Shimano shifter with a SRAM derailleur. Or maybe that's just true in MTB world and not road bike world, not sure.
OTOH, chain, cogs and chainrings are pretty much compatible, at least within the constraints imposed by the changes in chain width to accomodate the newer, denser cassettes. Eg, 10 speed chain or 9 speed chain won't work with an 11-speed drivetrain.