The first time I had to change a rear tire after a flat, the brake drum seemed to have gotten stuck inside the wheel and just popped off. A few weeks ago I had the tires rotated, so out of curiosity I removed the left rear tire and, once again, the brake drum popped off inside the wheel. Is this normal?
I, personally have never been lucky enough to have a drum just pop off. I usually have have to back off the adjuster a few clicks to loosen it up. Check the adjuster and make sure it can rotate, It may be froze and can't adjust the rear brake when you back up. This would leave a gap between the shoes and drum as the brakes wear down. The other possibility is corrosion between the wheel and drum causing it to stick to the wheel when you remove it.
By pull, do you mean to one side or the other? If so, then no. I am leaning towards the corrosion theory as to why they stick. We don't use salt on the roads up here in Fairbanks (too cold and dry), but we do have to drive through a lot of snow. The temperature range here in Fairbanks can be anywhere between -50 F and 90 F. I wonder if expansion/contraction may also play a role.