Wow, either you have a run of bad luck or you cheesed someone off in Houston
I just had to fly out LGA=>OAK and back tomorrow, last minute booking for around $300.00. As it stands now I'm 3 for 4 on the FC upgrades on this trip...one of the reasons I'll take CO every time from the NYC area.
P.S. I'm actually 4 for 4, when I turned on my phone on landing in HOU from OAK, I got a text that I was upgraded, that was nice. I guess it's easier to get upgraded on a late Thursday night flight than on a prime time one.. ^