One thing I have noticed is that beer that sits an extra week in the fermenter at fermentation temperature (not cold crashed) often clears up pretty well on its own.
I wonder if sometimes we rush things and package too soon. In that case, yeast may resist flocculation simply because there is sugar or other nutrients still in suspension. But, in that case, if the beer has been chilled and taken off the yeast the time to finish out the fermentation completely, which the yeast really want to do, gets way slowed down. The yeast in suspension will finish it off eventually and then flocculate but only when they are ready.
When I got a Tilt hydrometer I noticed that fermentation is not always over when I think it is. A lot of fermentations go really fast for 3-5 days and then have a very slow tail (several more days) where they drop 2-3 more gravity points over that extended period. I think the rule of thumb of waiting 3 days after the last gravity change works well if you take this tail into account.
Just a thought.