It might, or it might not go down in response to a lack of sales. Some airlines continue to segment their customers by elastic vs. inelastic demand. As departure date approaches their customer mix changes, and it might make sense to raise prices instead of lower them even if it leads to unsold inventory. After all there's a secondary market for unsold inventory - frequent flyer mile redemptions.

Its not as cut and dried as you're making it out to be.

It is accurate at the time presented. You can buy N seats for $X each, before the next seat is more expensive. That's all you can really ask.