As stated, there is a point that UA holds back more seats until airport check-in, resulting in no seat assignments being available for a non-elite flyer six weeks in advance. AA for example opens up damn near the entire cabin for everyone from day one.

The result is that shockingly frequently, as an AA EXP I cannot even score a seat assignment on expensive tickets, up to 4 weeks out. I'm sitting on one for Tuesday that I bought almost four weeks ago that I still don't have a seat assignment for (and EXP upgrade %s on AA have been dropping like a rock lately). Other consequences are that with less seats available to the agents, there is less they can do for families or groups that want to sit together because there's nothing left to assign.

I absolutely applaud UA's approach. AA has been infuriating me and several other elite flyers I know lately with this. UA's policy means that generally speaking, the more expensive tickets will get seat assignments, and the cheap seats get them on a 'first come first served' basis. UA is even generous enough to make this priviledge available for the very attractive price of $300/year. And worst case, on UA you can still get to the airport early to score some of the seats that haven't been assigned yet.

To the OP, and I don't mean this sarcastically, try AA. You will find seat assignments much easier to get in the exact scenario you are describing. It will be someone like you that denies an elite member on a much more expensive ticket a seat assignment, but that is how AA has decided to manage its business. So if you can benefit from it, have at it.