Unless the baseline is where the high performers are performing at right now.

It's a win-win for companies to hold employees to high standards. Either they sacrifice health, family, relationships, hobbies, etc. to meet unsustainable demands or they "self-select" and the company no longer has to pay their salary, healthcare, benefits, etc. In the economic climate we're living in, it just makes economic sense to squeeze as much productivity as possible out of your workers. This includes pushing already high performing workers to do more than they already are.