Walk-in theater

As drive-in theaters continue to close down, walk-in theaters (often on big lawns) are becoming more and more common, like Washington DC's Screen on the Green, playing tonight (and throughout the summer) on the Washington Mall. Here's my favorite example in Switzerland. Why the popularity?

Here's a comparison:

Cost:
Drive-in theater: Same as a movie theater
Walk-in theater: Free, usually sponsored by the City or arts group
Fresh air, space:
Drive-in theater: No
Walk-in theater: Yes
Maximum number of friends in group:
Drive-in theater: 4-5
Walk-in theater: Hundreds
Spontaneous meetings:
Drive-in theater: Maybe on visit to the bathrooms
Walk-in theater: Wide open
Picnic spread?:
Drive-in theater: No
Walk-in theater: The best part about it