Why can't TV commercial channels show all its ads before a movie like the cinema and broadcast movies without interruption?

Because they are paid more for advertising slots DURING a movie.

because people would change the channel or get up and do something else.

Perhaps you've noticed, when a commercial comes on and you change the channel

most stations are also playing a commercial at that time.

It's how they condition viewers. Grab your attention an repeat...

You know 'they got' someone if they start singing or whistling a commercials jingle or tune.

That person becomes a walking advertisement

$ .

So you can take a potty break or get a extra snack.

Because people would tune in when the movie starts and skip the ads

It would be easier for people to avoid them altogether.

cause they like to have all those interruptions

Many of the cable channels that specialize in movies do that quite a bit, now.

And no, I don't mean HBO or Showtime. I mean channels like TCM or AMC.