My son (18 months) and not yet walking properly hates the buggy. I manage about 5/10 minutes before the inevitable crying. All other kids look find in theirs, I don't get why mine hates his :-( Because he's not walking it's really limiting what i can do with him.
My 15 month old hates his buggy too and always has done. I carry him in the sling everywhere. He has just started walking which helps. I've had the same thoughts as you though, why do all those other babies/toddlers just sit happily in their buggies?!