@ocffzpc7zf9b While they're quite similar, iOS and iPadOS are not exactly the same, and they're diverging, meaning an app designed for both might require two sets of updates each cycle. And while it's certainly true that not everyone has a phone and a computer, I do believe that most people who have a newer phone or tablet powerful enough to run Sims 4 also has access to a computer. I'm not saying that covers everyone, only that it's enough of the potential market that creating several new versions of Sims 4 for mobile platforms would likely not be anywhere near cost-effective.
And remember that it's not only about the initial cost of a port but also the ongoing costs of adding new game content and maintaining compatibility with each OS as they change. The switch to the Metal version of Sims 4 for Macs was a significant undertaking, and EA has yet to release a version of Sims 4 written natively for ARM Macs, which are already quite common. The game does run well in Apple's emulator, so it's not a critical issue yet, but Rosetta 2 will only be around for as long as Apple cares to include it.
Steam Deck runs a custom Linux-based OS and when released may well be fully compatible with Steam Play, a platform that allows players to run Windows-only in Linux distros. Everything Nintendo is proprietary in both directions, so it's irrelevant. Streaming services work fine on phones so long as the gameplay is handled by a computer, whether one belonging to the user or one managed by the cloud gaming service, and Sims 4 would work on either, with no updates needed, as long as EA and the service allowed it.
For everyone else, Sims Mobile is available for people who want to play a Sims game on a mobile device. I doubt it will ever look any more like Sims 4 than it does right now, but that's fine, it's its own game and doesn't need to be anything else.