Why REBIRTH but not this on DVD?

I don't get it. The first two (out of three) of the REBIRTH OF MOTHRA films warranted a DVD double feature...from the same company that put them, and the original MOTHRA, on VHS. Yet the very first MOTHRA and the final REBIRTH film have been ignored. What's the company's logic on this? They've been trotting out a lot of the GODZILLA stuff, and Tokyo Shock has been cleaning up on Toho titles. I can see GODZILLA is the bigger name brand, so how did Sony/Columbia decided to pick the two particular Mothra films they did for DVD?