Where it's dry for long periods, yeah, pipes will dry out and the stems get tight. Wood shrinks when dry. So if it's super tight, you roll up a little 180 grit and spin it once or twice, takes very little to loosen the fit. Then in summer when it's 80% humidity for 4 months, the pipe will grow again and the stem may get a little loose, and bees wax etc will take care of it. Lots of places are hard on pipes this way, and it's nothing to do with leaving things out or twisting the wrong way or cleaning too often, it's just the wood moving.
The next question is "Okay smart guy, why does a loose stem tighten if you smoke the pipe?" and the answer is, only the wood near the tenon is getting wet - it expands but can only go inward, tightening it's grip on the tenon.