not that they are necessary, but when you are in a dark room and aren't continuously keeping your hands on the keyboard to type the backlit keys come in handy. When you are using the trackpad or reading something and maybe just need to hit a few quick keys for a shortcut or something it is nice to easily be able to see what keys you are pressing.
Why people on these forums can't see that just because they may not use a feature, doesn't mean nobody else does. (BTW, that's not directed at you, just the general consensus on these boards that if I don't use or need feature A, B, or C, then surely nobody else does

) Certainly almost nobody uses absolutely every feature on their macbook pro, but surely each feature is used, just by different "users" or "groups"
Some people may need backlit keys, some people may want an expresscard slot, some people may prefer firewire ports, some people may need an optical disc drive, others may not.... stop trying to tell people that just because you get by fine without a certain feature that surely they can too. I'm sure both users don't have the exact same needs from the computer as they likely are using them for different tasks entirely.