There was a time when coaches - literally - didn't let their athletes drink water because they wanted them to "get tougher." We now know that that's stupid. Well, most of us do, some coaches still do that because they're stupid also.
Running 300's is dumb because football players don't run 300's. There are better ways to implement conditioning. And when it's done right, it's always tough.
Trust me, making someone puke or feel like they're gonna die is easy. Making better football players is what you pay for.