SMS era Sega needed software and a lot of it so it was easy to do ports and also get around Nintendo douchebaggery. So early on in Japan it was a quick way to get some software out the gate to a hungry audience once the JPN version of the NES was known to be a hit, and later on much of what I said above. But either way as a computer retro type these ports have some upsides. Note that as a fell