You'll only find threaded BBs at C&L Cycles. This way of attaching bearings and an axle to the most-stressed part of the frame is a case of "why mess with success": big chunky screw threads in steel has a very long history of being constantly show to be the most reliable solution for sticking your cranks on your frame.
We and quite a few industry colleagues like square-tapered-axle bottom brackets since it's a lot easier to try different stuff, and while other crank standards have come and gone, you've been able to get square-taper parts for generations, and will for the foreseeable future. In the meantime Shimano developed Octalink (twice) and Hollowtech, and I'm sure they're a couple years away from a new thing, and SRAM seems to change BB standards every five years.
That said, in the interest of being able to use all the cool cranks we want, we're happy to stock a bunch of standards like Hollowtech, GXP, DUB, and 30mm.
