I think the problem is, the mics are set for television and the live crowd on hand can’t always hear. My wife and I went to Searchlight to hear Sarah and unless you were fairly close to the stage you would not have been able hear her well at all. But yet, when I watched her on TV later, you could hear her just fine! I suspect what they really need are better PA systems at these events.
The systems are probably just fine.
They need better sound engineers.
Then the problem is the man in charge of the sound system.
The people who are there in person are a drop in the bucket compared with the millions who will hear a sound bite on television. And if they hear screeching, they will be turned off.