Gaming

I mean, there's probably still some niche, but the niche can get pretty small.

Movie theaters kinda did this before the arcades did. Used to be that it wasn't normal to be able to watch movies at home, but once that happened, the space for movie theaters got a lot smaller.

https://en.wikipedia.org/wiki/Movie_theater

New forms of competition

One reason for the decline in ticket sales in the 2000s is that "home-entertainment options [are] improving all the time— whether streamed movies and television, video games, or mobile apps—and studios releasing fewer movies", which means that "people are less likely to head to their local multiplex". This decline is not something that is recent. It has been observed since the 1950s when television became widespread among working-class homes. As the years went on, home media became more popular, and the decline continued. This decline continues until this day. A Pew Media survey from 2006 found that the relationship between movies watched at home versus at the movie theater was in a five to one ratio and 75% of respondents said their preferred way of watching a movie was at home, versus 21% who said they preferred to go to a theater. In 2014, it was reported that the practice of releasing a film in theaters and via on-demand streaming on the same day (for selected films) and the rise in popularity of the Netflix streaming service has led to concerns in the movie theater industry. Another source of competition is television, which has "...stolen a lot of cinema's best tricks – like good production values and top tier actors – and brought them into people's living rooms". Since the 2010s, one of the increasing sources of competition for movie theaters is the increasing ownership by people of home theater systems which can display high-resolution Blu-ray disks of movies on large, widescreen flat-screen TVs, with 5.1 surround sound and a powerful subwoofer for low-pitched sounds.

Drive-in movie theaters got hit even earlier:

https://en.wikipedia.org/wiki/Drive-in_theater

Decline (1970s–1990s)

Several factors contributed to the decline of the drive-in movie industry. Beginning in the late 1960s, drive-in attendance began to decline as the result of improvements and changes to home entertainment, from color television and cable TV to VCRs and video rental in the early 1980s. Additionally, the 1970s energy crisis led to the widespread adoption of daylight saving time (which caused drive-in movies to start an hour later) and lower use of automobiles, making it increasingly difficult for drive-ins to remain profitable.

Mainly following the advent of cable television and video cassette recorder (VCR), then with the arrival of DVD and streaming systems, families were able to enjoy movies in the comfort of their homes. The new entertainment technology increased the options and the movie watching experience.

And, they apparently did a similar-to-D&B's, more-adult-oriented shift to try to mitigate losses:

While exploitation films had been a drive-in staple since the 1950s, helped by relatively limited oversight compared to downtown theaters, by the 1970s, several venues switched from showing family-friendly fare to R-rated and X-rated films as a way to offset declining patronage and revenue, while other venues that still catered to families, began to show R-rated or pornographic movies in late-night time slots to bring in extra income.[citation needed] This allowed censored materials to be viewed by a wider audience, including those for whom viewing was still illegal in some states, and it was also reliant upon varying local ordinances controlling such material. It also required a relatively remote location away from the heavier populated areas of towns and cities.