[Billthedrill]

Mankind has had the wheel for ten thousand years. Mankind has had luggage since somebody first sewed a sack together out of an animal hide. So tell me this:

WHY DID NOBODY THINK OF PUTTING WHEELS ON LUGGAGE??!?

(Sound of hyperventilating)

[TomGuy]

WHY DID NOBODY THINK OF PUTTING WHEELS ON LUGGAGE??!?

Because they didn't have to rush from Terminal 12 to Terminal 23 in 7 minutes because of a last minute change in flight numbers.

[Sherman Logan]

Wheels on luggage. One of the inventions that made men obsolete.

[TexasFreeper2009]

probably because for those to work requires a flat smooth surface everywhere you go with them. And until fairly recently most parking lots and roads were gravel.