There used to be a lot more independent movie theaters that would screen old movies on a regular basis. We don't really see that anymore.
And the screen to movie ratio was a lot friendlier too. These days it's hard for a theater manager to find a reason to keep a movie showing past week 4, back then they'd keep a hit in theaters forever. I remember the first Indiana Jones movie was in this one theater in town for over a year, then they pulled it for two week and brought it back for a "return engagement" for over a month, I think they were getting fresher prints, and that theater only had 4 screens. Of course back then there might not even be new movies released during the slow times (like February) and even a "busy" Summer blockbuster weekend would rarely see more than 3 releases in a week. Now they release 3 or 4 movies a week in the slow times and Summer is just psychotic. That theater that showed Indy for a year now has 20 screens and never shows anything for more than 2 months, they just can't spare the screen space.