On the 3000 and I thought the same applies with the 7000 this behaviour is settable

With my 3000 (well 950 UK model) none of the hard keys (except the ones on the left side) turn the backlight on. the backlight only comes on with the screen when you touch it. This is how I set it and you can change it.

On page 3 of the settings theres options for screen activation where you can set the cursor and firm keys activation (you can set to either send the code, turn on the light or both with combinations of the 2 little icons)