Because it's being directly tied to funding. Do well, more funds. Tests are low, less funds. It's completely ass backwards. Teachers aren't afraid of being graded, the issue is what's being done with that information.
The result you want from gymnastic coaching is well aligned with what the test measures because, well, the test and the desired result are the same thing.
This is not the case with standardized testing in education, is it? It's a lot like these tech interviews people keep complaining about that test a knowledge bunch of bullshit you have to cram for but have nothing to do with the actual job.