So here's my not-so-hypothetical situation. My wife and I are on an American Airlines flight and for the longest leg (~6 hours) there are only "Premium" economy seats and crappy (single middle) seats left.
I just got changed to this flight because of a night-before cancellation, so I didn't even have a chance to pick a good seat from the free options despite booking this trip 2 months prior to departure.
So here's my theory that I'm trying to validate/invalidate. If I don't pick a seat and let them assign it at the gate, it seems like the odds improve to get a "Premium economy" seat. My reasoning is that if I just pick a crappy middle seat from the remaining free options, that's exactly what I'll get. However, I'm betting that they hold back premium seats hoping to get people to pay for them at the last minute, and they are more likely to be open for people without assignments on a full flight.
Another factor is that my wife and I bought our tickets together, I don't how hard they try to keep people who are flying together (at least couples) seated next to each other, but if they do it would reduce the odds of us getting assigned a single middle seat.
Any insiders with American have thoughts on my theory and whether it increases my odds by not preselecting a seat assignment? Do they give any weight seating couples together on a flight?