Sometimes a package (airfare + hotel) booked on expedia, orbitz or travelocity is too good a bargain to pass up; you still get airmiles, but generally the hotel is "generic" no miles toward hotel programs.
If you fly to Las Vegas (or other gambling locations) regularly, even "low-rollers" will get their rooms free; so you are getting airmiles but no hotel points.
I did join the "Priority Club (Intercontinental)" only because of an air miles promo. I would have to stay too many times at higher cost than I would usually pay to warrant continuing with them for another year (not to mention the added fee for renewal.) [I know free upgrades and other bonus promos are nice; but I can "live" without them ]