As an SLF, I just want to comment on why people do bring some things like razors on board - if you're on a late night flight into, say, STN for an early morning onward connection and then discover that (a) your bag wasn't tagged at the originating airport and (b) everything is closed at STN overnight then you start to wish you had a little bag of essentials to make an overnight at that rather chilly establishment more bearable.
This is of course a completely fictional situation
If loss of luggage wasn't a frequent occurrence people wouldn't want to bring most of it into the cabin - it's a pain in the ars* to lug about.
Just a thought.