Yeah it’s an interesting though. There have been a few that I can think of for me over the years:

1) Wouldn’t have visited Seoul for 22 hours a couple years back (to break up SIN - US) if (a) wasn’t a DL loyalist and (b) they hadn’t killed the NRT mini-hub that I used to transit

2) My first trip to Tokyo and Bangkok were driven by the fact I was a 1K at the time and I was trying to maximize my F award down to Australia and 23 hour layovers via NRT and BKK gave me F the whole way and then NRT on the return to get on NRT - IAD back home. I fell in love with Tokyo/Japan during those two <23 hour layover and have been back a number of times since

3) For the last few years out of RDU if you are going to/from Europe you are either a DL loyalist connecting via CDG (like me) or an AA loyalist connecting via LHR