Seems like 90% of the machining projects i look at use socket head cap screws. They are also used on most lathes that I see, and on tool holders etc. On my lathe the carage lock screws are socket head cap screws and they are always filling up with swarff making it hard to get a hex wrench in there. It is easier to strip the socket head on a socket head cap screw than it is on a Robinson head and a normal Hex head doesn' get filled up with dirt. I had to replace the screw on my screwless vise and on several of my quick change tool holders for this very reason. I replaced them with normal hex Heads. So why are they so popular?