A long-haul flight is so much more pleasant with wifi. There's only so many movies I can watch (for me, 1 or 2) before I get bored out of my mind.
It can get lonely on a plane if you are traveling alone. The people around you aren't always willing or able to talk (they may be asleep, don't speak English, or are preoccupied with a movie), so you may end up sitting for extended periods with nobody to talk to.
Being able to chat to friends while in the air makes the experience more comfortable than any seat ever could.