Data point:
I got the 1K/3K offer. Im a 1K. Same EQMs as I was at this point last year (about 68K). When I thought about it, I found I have not flown any other airlines during that period although I would have liked to a couple times but stayed loyal to UA. Phooey! Dont have any idea why they offered it to me.
Im based out of SEA but fly SEA-IAD-SEA 95% of the time. Maybe since I fly the same route all the time they assume I am only using UA for this route and must fly other places?