Do you work in Film? If you did, i think you would understand that million of dollars can be lost when a Director is unhappy with a finalized sequence. Everything must be redone, and re-rendered. Previs enables the director to see their vision, at a close enough quality level, at a much lower cost. If you have issue with the fact that the final product is not good (in your opinion), then the blame lies on the Director/Creators. Previs is just a tool.

Helps the Director to share his vision, Helps the Director and DP be on the same page, helps them know what effects will be practical and which will be CG, this way they know how to prep the set & how to more accurately budget. Can help the Director find his vision.

It makes the movie real to investors, so that you have more backing and belief in your project.

There are many other benefits as well.

There were a lot of sequences that looked like they belonged in Video Games before Pre-Vis became a separate industry.

Some Video Games have Great Sequences that are better than many movies that don’t use pre-vis.

All those sequences you don’t like, would have still looked the same without pre-vis, because that’s what the director wants. It would have just took a lot more time and money, because they would have been trying to do it all in finals.