Yeah we do.
If you're training hard your gear's gonna get sweaty, but what do you do with that sweaty gear on the ride home?
Toss it in your backpack? Mmm... B.O.-laced nalgene... not to mention grossed out friends. (4-legged and otherwise)
Seal it up in a plastic bag? Your friends are protected, but your gear will stay wetter longer, and you'll pay the price when you get home.
Now there's a third option. Throw that sweaty gear in your Greatest Ultimate Bag's Iso ventilated compartment - seal it up when you're in close quarters, and unleash the beast while you're walking around.
Finally you can air out your gear, without grossing out your neighbors.
Spot thanks you.