All you need to do is have one trip where there is a missed flight or something is closed or you are otherwise delayed. And then you are looking at a bunch of cascading change fees (that can add up to astonishing numbers rapidly) and being on hold for most of an afternoon, at best.
I had a ski trip to Banff where a two-hour delay ended up costing me about $1500 between needing to book another hotel, losing our rental car reservation and needing to rent another one, and the nosebleed change fee our hotel in Banff charged me. For two freaking hours.