The "General Games Chat" forum, which includes Retro Game Reviews, has been archived and is now read-only. You cannot post here or create a new thread or review on this forum.
You relese a game it sells well-You make money
You realise that the game genre is fine so why risk a change?
You produce small changes to the game and resell them as "add-ons"
You make even more money.
This is why they do it. Most game developers have no consience.