In fact, many times they're even asked to do so by moderators when they think it'd be a good idea.
There's nothing wrong with using it to hide your browsing habits or reduce tracking, but when you're signing up for cloud services, you're presumably already supposed to be providing your identity at that point, so that use case is moot. Someone could be stealing your identity and using it to sign up as well. Imagine the crimes you could be framed for in those situations.
It would be hard to keep the service cheap if there were a greater risk of bad actors using it.