In this economy, I have noticed that all of the airlines are releasing fewer seats for complimentary upgrade. I have gate danced quite a bit this year, with varied success. That's just the way it is.

Airlines want to sell the seats, not give them away, especially on transcon routes, where there is higher demand.

Keep in mind that complimentary upgrades are based on availability in that fare class. If you purchased coach, then that should be what you expect. A complimentary upgrade is a gift, not a given.