But if that was the case, they would only have to release a single-player only version. They wouldn't have been the first company to do so. It would still sell millions.
Though the same can be said about hundreds of third party games. It would be interesting if we got more information from publishers on why they don't bother with the Switch. Is it because they think they can't sell on a console monopolised by Nintendo software, though that seems like a self-fulfilling prophecy. Is it because PlayStation/Xbox/PC is a lot easier to develop simultaneously for?
I'm sure there's several different reasons but case-by-case it's hard to rationalise why they wouldn't do something like a GTA V SP port. I'm surprised we never saw The Sims 4 for Switch also.
From Microsoft, they released this to CMA showing 2021 sales. Nintendo Platforms are only responsible for 18% of 3rd party unit sales while having a massive install-base. If it wasn't for a massive 3rd party exclusive like MHR launching in 2021 it'd probably be much worse.
To be honest, that's honestly not too bad. Switch is almost the same as XBox, and XBox is heavily driven by 3rd parties and gets almost every major 3rd party game whereas Nintendo doesn't.
That's still a sizable chunk of the market, Nintendo just needs to make it easier to port games if they can, that to me seems like the main hold up (it's not worth the squeeze).
And the counter point too would be that the Nintendo 3rd party figure is held down because they often don't get a lot of the major 3rd party releases. If Resident Evil 4 Remake was on Switch for example (putting hardware limitations aside), I'd buy it, so would probably a lot of people.