Brentwood releases can be "gray-market", which means they've probably slipped into public domain or no one's sure who the rights holder(s) are. That's been an issue with a lot of these movies. It takes a lot of effort and cash to track some of these down with all the years of haphazard releases.

I'm so glad Grindhouse did for this one as well as all their (hopefully soon) upcoming releases. Love these guys.