Sorry, just a random gamer, not a developer. Also, the game developers do not work here, EA's community managers do.
But The Sims 4 for PC is now more than 3 years old, and the console version just came out. To make the PC-version work with a controller they would have to remake lots of things in the game no? Just like you cannot play The Sims 4 on PS4 with a keyboard and mouse.
Making the game available to play with different controllers is not just to check a button in the "game creator program", it's advanced and needs lots of work, and I don't think the demand for playing The Sims 4 with a controller is very big, as it's a game that typically is a lot easier to play with mouse and keyboard. If it was a racing game or something like that I would think that it might be a bigger thing for EA to prioritize though, and the demand would be greater.
