Then I guess you aren't familiar with the 20 minutes of trailers, 1 minute of Cocacola ad and 2 minutes of other completely irrelevant content before the movie actually begins.
Fwiw I always enjoyed the trailers at the movies, no the other ads I could very much do away with (and I used to purposefully come late to shows to miss the ads).
If the whole preshow is 10 minutes like in the theater where I used to live a few years ago, that is still somewhat more acceptable. But these days, with 20-25 min of preshow, were I to arrive at the showtime, I'd be looking at spending 1hr extra just to see a movie compared to watching it home (consider the time it takes to travel and maybe wait in the line for concessions).
I'm sure that's what lots of people do and many people are totally fine with this. Not me. I have got too much going on to spare that 1hr, especially on a weekday evening. I have to intentionally leave late to arrive on time to justify even going to the theater at all.
And then wonder why people don't go to the cinema and wonder if they can increase the amount of ads to compensate...