Depends on who you ask. I know a bunch of people that roll or stuff tubes. Some stuff says it's all natural, nothing added, some doesn't. If you've ever shreaded plain, uncased, all natural tobacco you might find the result repulsive. Also, I understand that the papers and tubes may or may not have chemical stuff in them. Most paper is bleached. At the least.
They're probably better off loading their own.
At least you can see what's going in the tubes when you load them yourself.