There's lots of reasons people 'cheat' in games. In this case it might be:
• You enjoy playing Pokemon but you don't want to or cannot find the time to grind out the few hours of leveling up you need to progress, or to find your specific favourite handful of Pokemon, so you use a device like this to save yourself some time.
• You want to succeed in the competitive space (yes, competitive Pokemon is a thing[0] and is ongoing right now in fact[1]) and you don't want to grind for Pokemon with specific Effort Values, which are the randomly generated numbers that effect how strong your Pokemon attacks are. So you use a device like this, though probably altering a save file would be just as easy and not detectable by Game Freak/The Pokemon Company.
• You don't really care about Pokemon, but you know you can sell Pokemon on eBay[2], so you automate it with a device like this.
> You want to succeed in the competitive space (yes, competitive Pokemon is a thing[0] [...] and you don't want to grind for Pokemon with specific Effort Values [...]
I just want to point out, if you're like me and sometimes enjoy competitive Pokemon without grinding, cheating, playing the story or even owning a device, you can play online a simulator, from which every possible, grindable setting is just a click away. [0]
It's pretty popular, with it's own Elo, tournaments, online community etc. It's pretty fun, I can recommend it.
> You don't really care about Pokemon, but you know you can sell Pokemon on eBay[2], so you automate it with a device like this.
People who are selling Pokémon on eBay are probably just hacking them in rather than going through the trouble of using a device like this to obtain them “legitimately”
Many people play competitive pokemon. Pokemom randomly generate with different "IVs", meaning different attack/defence/speed/etcs. To get "perfect IVs" takes hours if not days of searching. Many automate this process as all they're interested in is the competitive game; not catching/hatching the perfect pokemon.
I've built something similar close to ten years ago for Generation 6 Pokemon games on the 3DS. At the time that meant soldering to a bunch of test points to send inputs.
Why? Mostly because it was fun and a good learning expereince. I barely used the Pokémon I obtained, but I did use them to build a competitive team.
• You enjoy playing Pokemon but you don't want to or cannot find the time to grind out the few hours of leveling up you need to progress, or to find your specific favourite handful of Pokemon, so you use a device like this to save yourself some time.
• You want to succeed in the competitive space (yes, competitive Pokemon is a thing[0] and is ongoing right now in fact[1]) and you don't want to grind for Pokemon with specific Effort Values, which are the randomly generated numbers that effect how strong your Pokemon attacks are. So you use a device like this, though probably altering a save file would be just as easy and not detectable by Game Freak/The Pokemon Company.
• You don't really care about Pokemon, but you know you can sell Pokemon on eBay[2], so you automate it with a device like this.
[0] - https://www.pokemon.com/us/play-pokemon/pokemon-events/pokem...
[1] - https://worlds.pokemon.com/en-us/
[2] - https://www.ebay.ca/itm/225598189077