USM is just DLC for an incomplete game and the DLC doesn't even complete the game.

Don't buy USM. If you want it, pirate it, but you already spent money on it when you bought SM.
If you buy USM, you don't deserve the $40 you spent even less than gamefreak.

Give me ONE good reason why you would buy the game rather than pirate it.

No, your "bros" aren't a good reason. They're just a series of numbers. Stop being autistic