Molgrips, it ain't no illusion. Look at the number of people on here who are constantly changing, upgrading and swapping their bikes, or parts thereon. Look at the threads on here about HT11 BBs! Read your average bike mag, and the comments along the lines of "if you're still running X, you might as well be filling your tyres with builder's sand and oiling your chain with glue". Yes, most people learn to take it with a pinch of salt, but it's still annoying.
What's not to like?
Not having to carry two humungous spanners around in your toolkit, for starters. Have to admit that none of those bikes would look "right" with a threadless stem though.