In the small town where I live we have a small cinema with three screens. They always start the movie at the advertised time - no adverts, just a few trailers in the preceding 10 minutes. You can book online, but I usually just walk in and buy a ticket at the desk. The seats aren't assigned, so you can pick whichever you like.

Occasionally I have a "private screening" where I'm the only one in the auditorium. The most recent example was "The Mummy". I hadn't fully thought throught the implications of watching a horror movie alone in the middle of a darkened 65-seat auditorium!

There's another town a few miles away where a similar cinema has both assigned seating and 20 minutes of adverts before the movie.