Depends how you look at it. If they don't charge to change the flight, they lost $200 or whatever. You made a choice; you purchased a lower-priced fare with a change fee, because you felt the odds work out very favorably that, even if you had to pay a change fee, you still come out ahead when averaged out over several flights that you didn't (have to pay a change fee).

If flying domestically, you also made a choice in favor of what you see as United's "unique selling proposition" over Southwest, which allows you full credit towards a different flight.

When we make demands that the rules don't entitle us to, and adopt the "hang up if you don't like the answer" way of doing things, we're showing disrespect to the person at the other end of the line who's job is to assist customers, particularly when we act as if we're owed something this time because UA has treated us so badly elsewhere.

And then we wonder why it's tough to train employees regarding the rules, when they're being confronted daily by customers who claim to know the rules better than they do. Not saying it isn't sometimes true, but it doesn't take a brain surgeon at the UA end of the line to know when someone is trying to get something they're not owed.