For me it's compatibility, mostly. And because I do my own wrenching on all
of my bikes, I like the idea of accessibility of parts over the years because it's rare that I'll sell a bike that I've built up and used. If a BB standard isn't picked up by a number of makers, the less likely it will be to find a part in the future.
A metaphor would be if you buy a car and instead of using one of a few standard sizes of fuel pumps, it uses a slightly odd shaped fuel pump that requires a special shim if you'll use another fuel pump. The car maker reasoned that their fuel pump is superior... when, really, it's not any better compared to a different fuel pump that is more standard across manufacturers. Yes, driving the car you won't have a problem. Then one day you'll want (or need) to replace the fuel pump... but, darn it, it's a proprietary fuel pump and not readily available compared to other pumps. If you use another pump, you need a shim which is also hard to find. So you're left paying $$ for an increasingly rare part.
Same issue with Specialized's OSBB vs. BB30. They are not the same, but darn close. Specialized is being stubborn and they just want you to use their own cranks (which are good cranks, but that's not the point). Then there's Cannondale sticking with BB30 and not PF30 - the latter has better manufacturing tolerances, which would also help bring Cannondale's cost of manufacturing down a bit. But, no, Cannondale is also being a bit stubborn on pride. So we as a consumer have to go along with the stubborn pride issues of a brand? That's great.
The next carbon frame I purchase will probably be BB386 because it seems to be the most
option compatible while allowing for the increased stiffness and weight loss, but for now it's all reliable BSA. Even a frame I recently spec'd, ordered & received is a reliable BSA frame. But the topic of BB superiority is for another thread
|| Other projects in the works.