ELI5 How come streaming service are now running commercials? Is that not bad for business because most if not all people got it to avoid commercials?

The line always has to go up. If the company stops picking up new subscribers, then their profits stagnate. And that makes investors unhappy. So to avoid that, they start to jack up the price to keep the line going up. And if that isn't enough, they then start throwing ads into the services.
The line must always go up.