Not everyone likes the BB30 standard. But they want to buy a frame that has a BB30 bottom bracket shell. No need to despair, get the frame and then purchase SRAM's BB30 to BSA Bottom Bracket Adapter Kit. Once it is pressed into the BB30 shell, your bottom bracket will function like any other English-threaded bottom bracket. Install your favorite external bottom bracket, your favorite internal bottom bracket, maybe even an old-school Campagnolo loose-ball bottom bracket so you can run your cold-forged box-section 144mm bcd Campagnolo Record crank with the cool pantographing.
This isn't an easy home install, so you might want to take it to a shop. Claimed weight of the SRAM BB30 To BSA Bottom Bracket Adapter Kit is 60g.