Who are 'they'? It might be that teams come from a more rigorous environment with project plans and imposed rules and were never given the chance to experiment with how they create software, or they might come from an environment without any rules whatsoever. Both work for a lot of companies, but usually you try something like Scrum because they don't.

A lot of times it requires a change of mindset where managers and executives have to relinquish control and trust developers to do what's right. That might not be the easiest thing in the world.