well as someone rightly pointed out (and lo and behold, he doesn't seem to be a singaporean), this could because of safety reasons
like a disclaimer, that they are not supposed to do it and if they do it, it's their pasar if the airplane goes into turbulence and they're doing the dirty and end up with broken this broken that.. anything can be broken, including the penis y'know
same like how some gyms make an induction course mandatory for their customers.. do you think they really care whether the stupid chap knows how to use a machine he'd probably never use? no, it's just in case the stupid bugger goes and gets his hand stuck underneath the weights.. then can say horhor, see i told you not to do that BUT YOU DID, serves you right and we are not responsible
the cabin crew can see into the suites. they have some kind of screen thing over the windows, but it can be seen through when you're near. they can't give total privacy because of security reasons. :devil::devil::devil: