Another SFO based 1k anecdote. I'm around 20-25%, with low fare class (K or lower) with primarily Mid con (ORD, IAH, AUS) and Transcon (EWR). The only upgrades I receive at the upgrade window are short hops (SFO-LAX, SFO-BOI).

United has been successful in resetting my expectations. I do not expect to be upgraded. My objective now is to have a exit row/economy plus seat with the middle seat open.

While do not fly DL as much, my upgrade % is about 60-65%, including a couple of SFO-ATL flights (as a Platinum).