By itself, law essay writing as a service doesn't seem (to me) as a violation of their terms of use. There are a lot of use cases for producing web content/copy for websites, magazines, and the like that have absolutely nothing to do with education.

As an example, would "business plan writing" be a bad service to offer? What if an unscrupulous MBA student paid to have someone write a business plan for a college class?

I think this is mostly a non-issue and it seems like you have a bone to pick with upwork. What's the real story? Why do you hate them?