I don't know why I'm bothered!
My friend's daughter does it as soon as she walks in and for some reason it annoys me to no end. I don't say anything to her, just usually will ask if she's hungry.
I do offer snacks periodically when DS has friends over and of course I wouldn't mind if any of them asked me for a snack or drink.
I think it's just that I was taught that this was incredibly rude- my parents would have been mortified if I'd done it- and it's stuck with me.
Anyone else bothered by this or am I being terribly unreasonable? :o