The big networks filter such traffic, the small networks benefit from it.
https://www.reddit.com/r/legal/comments/1pq6kgp/is_it_legal_...
You may also get accidentally get your own website blacklisted or moved to a lower RPM tier, or provoke shadow-ban websites that you like to visit, or... generate more ad revenue for them.
If you intentionally loop-download large files or fake requests on websites that you don't like, in order to create big CDN charges for them, then what ?
Without reaching the threshold of Denial of Service, just sneakily growing it.
Nobody benefits, except for the weird idea of the pleasure of harming people, still illegal.