Some IP holders do sue. Banpresto sued a group making parody footage of their flagship game because the group was immensely popular and was making $x00,000 per

Some IP holders do sue. Banpresto sued a group making parody footage of their flagship game because the group was immensely popular and was making $x00,000 per event. Basically, as long as you aren't overly successful, they won't come after you.