Not only are they less crowded and attract a (how shall I put it?) more sedate audience, but they also tend to be cheaper. If you want to avoid lines and take advantage of discounted tickets, go catch a movie before 2 p.m. (a morning show is even better) or a Tuesday night showtime for example.
There are no guarantees, of course. I've been to matinees with crying babies, which are worse during a movie than chatting teens in my opinion, and I've been to near empty weeknight screenings during which the only two other people in the theater thought they were re-enacting Mystery Science Theater 3000, commenting on every single thing that appeared on the screen. But the odds are still in your favor that you'll probably have a better moviegoing experience than the packed weekends.
Some people, on the other hand, love the excitement of seeing a movie opening weekend with near-crazed enthusiastic crowds. That energy definitely adds to the fun sometimes, but it's not for everybody. So those of you who haven't been to a film theater in a while and dread the noisy packs of folks who go on Friday and Saturday nights, remember that there are days and times that will give you more breathing room and peace of mind.
Go, my friends, see a movie on the silver screen. It's still a much more amazing, immersive experience than watching a flick on your TV amid the distractions of home.