We never buy it, and think overall through the years we've come out ahead. Both our companies are very reluctant to have an employee cancel a vacation (They do what they can to let you go when you've scheduled something in advance / are very big on that.) Also, our relatives are all in pretty good health, and we aren't anticipating any medical issues, etc. / deaths in the family that would interrupt anything. Anything like that would be quite sudden and unexpected for us.
I'm with you, though. We love Southwest's change policies (a breath of fresh air compared to other airlines). Unfortunately there are lots of places that Southwest doesn't fly. For Orlando, though, seems like I'm always using Southwest point to go there.
It's very much a question of how much risk you are willing to take and how you would feel about losses due to cancellation if you didn't have insurance. We tend to self insure low risks that we could easily with vacation or emergency funds financially absorb.
A typical vacation for us costs maybe $5000 - $7000. About half of that is perhaps non refundable airline tickets and a non refundable condo. This is not for us an amount high enough that we'd take out an insurance policy for. If we couldn't travel the week we planned, it's not like we could just do another week that year either. We usually do our biggest vacation each year, for example, over spring break, and another week would mean kids missing school, something we don't do or going in the summer (usually places we go in the spring are places we wouldn't even be interested in going in the summer). lol DH and I aren't keen on heat and humidity and like places like Orlando Nov. - April only. // And then, the following year we have a whole new vacation budget for travel, so it's not like a canceled vacation would be missing any sort of once in a lifetime opportunity.
For something like having to leave while on vacation for an emergency at home, that's one of many reasons that I have emergency reserves that we fund. I'd use those for something like that.