I think it's likely just coincidence -- they figure if they blast out enough emails masquerading as large companies they'll find at least a few people to grab the bait.

I mean I swore I'd never fly Delta again in August of 2004 and the spam filter has caught countless similar "Delta" confirmation emails, plus one every now and then from Southwest (last flown ~2012, not even a RapidRewards account), oh and Emirates procurement desperately wants a copy of my company's latest Catalogue and price list for a valuable partnership opportunity (at least twice a week) -- oddly I can't remember the last time I got one pretending to be United (but United does a good enough job with spamming me itself -- the hotel booking, cruises, rental car, credit card...)