frelkins,

Since carry-ons are fewer and lighter (to lug around) than checked baggage, and it takes quite a lot of time to retrieve your checked baggage, there is actually tremendous incentive for people to take only carry-ons with them (especially for short trips). Plus, there is no risk of lost baggage in such cases.

I would rather spend 5-7 minutes waiting on my seat in the plane or standing in the aisle (I don't get out in the aisle unless I am sitting on the aisle/middle seat, and even then I ask the passengers in my row if there really would rather stand and wait than sit comfortably) than wait for 20-30 minutes in the baggage retrieval area waiting for my suitcase.

A related factor that has been mentioned to me is that after sitting in their cramped seats for quite a while, many people just want to stand up and get the circulation going in their legs. They don't really mind standing and waiting.