Do people really just show up and hope for the best anymore?

The "box office" is not even really a thing anymore at most theaters. And the single person you talk to inside that is the "box office" just uses the same system you can reserve seats yourself on your own time?

Pretty much every theater is reserved seating these days. Why would I risk showing up last minute on a whim and end up in a horrible seat near the front of the screen?

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.

Mostly because unless it is a really desirable movie, hoping for the best has an expected outcome close to the best.I am a planner in most things, but for movies, it often simply does not matter.