Why are BNC connectors "the standard" for QRP HF radio use? Who decided, and why?
My QRP connector of choice is the RCA (more commonly known in the UK as "phono") connector. They are cheap, small, and easy to assemble, and one size can be used with standard RG-58 or miniature RG-174 cable. MFJ uses one in the small Cub transceiver, and I seem to remember that Heathkit used them at frequencies up to 145MHz and powers of up to 100W. You can get gold plated ones if you want to be flash, or want to minimize losses. If you're a cheapskate, you can salvage them from old audio equipment.
The use of BNC connectors and other types designed for use at UHF where losses can be significant is completely unnecessary at HF. QRP is supposed to be about "doing more with less" and I think using RCA connectors fits that description admirably.