For as long as I can recall, Southwest has held its prices high for peak travel times until the last few weeks before travel. Then and only then will they relent and lower prices if needed to sell all their seats.
Maybe other airlines are dumb, or maybe they have more accurate projections far in advance of how many seats they will sell.
Took two months from schedule release for them to open WGA fares on Sunday after Thanksgiving for something as simple as DAL-HOU. WGA fares dropped lower one month later.
For whatever that's worth.