WN is a totally different can of worms. They also don't allow standby on discount tickets. A colleague of mine who kept touting WN's "no change fee" policy was recently burned by a $150 upfare to come home just a few hours early from a meeting. The same change would've cost $25 on any major carrier, or $0 if you play the standby game.

So the next trip, they pay WN extra to get a refundable/changeable ticket so as to avoid this issue again.

I'm thinking that when you combine the high fares that WN typically has (they're seldom the cheapest), the upfares for standby or going home early, and now people paying extra on the off chance they'll want to change and come home early, the occasional $100 change fee a traditional carrier hits you with balances out in the end.