Think about and research all of the above questions. We will focus on the first two concerning theatrical distribution in this post.
1. Studio contracts with distributors (or worse yet studio ownership, ruled a monoploly in the 1930's but coming back, like so many bad ideas, today).
2. Distribution agreements that say you need to put one or a few screen s up with a film that is less tent-poll and more adult or indy.
3.Pressure from studios for a film to earn the maximum amount the first weekend...promoted and advertising cost are high, as are the cost of dominating screens.If a film does not make large dollars its first weekend it is considered a failure, no matter how good a film may be (or how valuable to the arts and to society.
4. Audience demand, which translates into the most popular among those sold on going by studio marketing and advance pubicity, leaving a small segment of the potential audience rush to the theater opening weekend at premium prices.
5. The need to make money fast and keep it flowing in the distribution industry, which has seen loss by the narrowing of distribution window before films go to DVD / BlueRay / Digital and later going to Netflix or Amazon. So the money has to come fast.
6. The cost of real estate and leases are up, so movie theaters have an intersts in filling the most seats at premium prices they can to make their bills and eventually a profit. It is assumed that tent-poll highly promoted films will bring in a larger, more excited and eager to spend audience.
If you know of or can think of another reason certain films dominate the number of screens opening weekend and/or stay on screens longer, feel free to post your ideas below in comments.