Why are shadows so performance expensive?

Noticed it first with BeamNG, then everything else afterwards. With shadows off I can max out everything else in BeamNG and get 60 fps, can barely hold 25 with them on. Why? And is there a way to fix that?

 

Your PC simply might not be able to handle them. You can either turn them off completely or turn on partial shadows if you don't like how no shadows look.

 

There is no performance difference between partial and all shadows.
I probably should've posted this in support instead of offtopic

 

What about no shadows? It should work then.

If it's still laggy then it's possible that it may not be shadows causing the lag.

 

"With shadows off I can max out everything else in BeamNG and get 60 fps, can barely hold 25 with them on. Why?"

 

Oh sorry forgot about that. Seems like you'll be better off leaving them off, even if it isn't exactly pleasing to look at.

 

Posting your GPU and CPU specs would be helpful to determine if there's anything you can do.