For short haul, the buy-the-cheapest-and-throw-it-away approach is what my company demands and it seems to work (sort of).

But for long haul we have the choice of flexibility and I sometimes use it and sometimes don't depending on the circumstances - an example of when it was worth it for me occurred last year. I had to go to Monterrey (Mexico, not California) at fairly short notice. Booked a return fully flex ticket via DFW connecting into AA. The day I arrived the local drugs folk fell out and 52 people were killed down the street from where I was staying. I decided to leave as soon as I had finished my business, pronto (yeah, I'm chicken). One quick call and I was coming back a day early, through DFW then onto IAD and LHR as all the BA DFW-LHR flights were full. No problems, no extra fees, just yes sir we can do that..... worth a bob or two.