You can install unofficial skins made by other users (or make your own), and ofc you can pirate/emulate any game you want in the GBA/DS/DSi/3DS line. There's other stuff too but that's the main pull for most people. With the eshop shutting down soon, this would become your only way to get new games unless you only buy physical copies.
Re: I hacked my 3ds!!
You can install unofficial skins made by other users (or make your own), and ofc you can pirate/emulate any game you want in the GBA/DS/DSi/3DS line. There's other stuff too but that's the main pull for most people. With the eshop shutting down soon, this would become your only way to get new games unless you only buy physical copies.