Admittedly, my desktop keyboard is backlit (I had to buy a gaming keyboard to get the macro keys I wanted), but the only purpose of the backlight for me is to know which of the four keyboard profiles I'm using -- and this feature isn't on many laptops at all.
I've been practicing by my work (as a programmer) and actively learning it aside -- typing without looking, and I am damn good at it.
There are however different use cases. Sometimes I have long reading sessions. Suddenly I decide the story is too big and want to stop reading it. Or I try to find a keyword in it. Or a hundred more things.
If I am to use programming terms, it reduces your bootstrap time when you want to use the keyboard after a period of inactivity.
...That, plus the fact that most are gorgeous and simply very nice to look at. There are definitely aesthetical factors as well, won't deny the facts. So it's 50% subjective, no doubt.
For example, I use the backlit keyboard when I'm debugging at night, because hitting the wrong key carries a penalty, and F9 is not nearly as heavily used as 'A'