As I understood it, IMHO is the place for polling:
Lately (and perhaps not-so-lately), I’ve been coming across threads, some of which appear to have been open a long time;
What’s your favourite poem?
Finding Cecil Adams and the Straight Dope message board (definitely a poll inside)
Have you read every one of Cecil’s columns?
In the last one, AETBOND417 pointed out that maybe this one should be in IMHO, but it’s still sitting there in MPSIMS?
Strictly, yeah, IMHO is the place for polling.
It’s just that those damn MPSIMS moderators are real slackers. Well, not me of course. But that Beer fella, whutshisname?
Also, the border between MPSIMS and IMHO is less rigid than, say, the border between ATMB and the Pit.
All IMHO, of course 
The mods and admin are humans, and if nobody really cares about the position of a thread, it tends to stay where it is. Of course, manny is pretty good about keeping debates out of GQ, and Tuba is the queen of the quick boot to the ass due to her experience with personal attacks posted on the ATMB (plenty of them directed at manny, for some reason ;)). Those are responses to activity that really threatens the integrity of the fora. Having a few polls in MPSIMS is hardly an emergency.
It can also be a real pain in the ass to move a thread. I’ve seen it take more than ten minutes on occasion. So, if the board is running slow, or I don’t have a lot of time at the moment, I’ll just leave a thread where it is. I’d rather devote my limited time to pissing out fires, deleting copyrighted stuff, editing spam, or other things, that I feel are more important than the actual forum in which a questionable thread resides. And lastly, like Coldfire says, the demarcation between IMHO and MPSIMS is a bit spongy. Even he line between IMHO and GD is a bit fluid at times. It’s all a judgement call.