You’re obfuscating the fact that those emulators are only or primarily used with pirated content.Technically emulators have no content in them, and the community generally doesn’t charge for them, so no money to be made there - just for fun and “love of the game”.
As for Nintendo (in particular) and Sega they are very careful not to drive people away from “new” product. Nintendo could make a boatload on old IP but they generally choose not to. Nintendo could literally re-release every system they have ever made and people would gobble them up like hotcakes.
The owner of the intellectual property and only that owner should have a say on how that IP is sold.
Taking a joy ride in a car you don’t own is grand theft auto.