Valid point - but do you need to tweet, check-in on Foursquare, and check email constantly throughout the day?
I do usually use my phone to check for restaurant reviews though, or product reviews if I'm in a store. Google Maps is also extremely useful. I see no reason to eat shitty food if there's a good restaurant just down the road. Unfortunately, most restaurant rating services (like Yelp) aren't too accurate these days.
The scores are, but in aggregate, I have a decent experience with Yelp reviews. As with any user-generate content, there are plenty of opinionated idiots, but I can generally quickly skim them to find out if they're an idiot or not and discount their negative/positive ratings.
It would be awesome if phones transformed into computers, sort of what Ubuntu has planned out. http://www.ubuntu.com/devices/android
If you're not in a position to pay for an expensive cell phone plan, or if you'd simply find the money better spent elsewhere, then do that. When you ask me if I "need" to use my smartphone, you sound like my mother. Don't do that.