It will take far more then ten minutes to film this. The actors may nail line #1 and #2, but flub #3 or #4, or #7 or look at the wrong thing, or the director won't like something about their emotions, or whatnot.

You have to do an entire re-take, whenever one little thing doesn't go as you want.

Compare that to a short-shot film. Have each actor fire off twenty takes of their four second line. If they got tongue-tied on the pronunciation of supercalifragilisticexpialidocious, they didn't waste an entire take.

Hell, with short shots the two actors don't even need to be in the same building for filming a scene, let alone on the same set at the same time. Do takes for one on Monday, do takes for the other one on Tuesday. It works better for everyone's schedules, and we can't afford to pay Scarlett Johansson to hang out on set any longer then she has to. Three months later, the director will decide that they really hate one of the shots, and it can be re-filmed during post-production.

The reason that this happens is because filming is expensive, budgets are bloated, celebrity actors command multi-million dollar salaries, editing is easy, and audiences will happily lap up action schlock like Michael Bay's Transformers (With its average of 3.2 seconds per shot.)

My SO works in musical theater. They don't have the privilege of stitching together a show from perfect four second intervals. They have to perform it right from start to finish - a two hour ordeal. This requires many, many weeks of grueling rehearsals... And each performance has many, many mistakes.