I can't speak for anyone else, but for me gaming is basically portable or not at all at this point. At home it's me, my wife, our two kids, and one TV. The chances of me getting that TV to myself consistently enough to finish a game are near zero. In theory I could use my PC since it's perfectly capable, but I don't like it as much as I used to. I generally don't have large chunks of free time to devote to games, instead I have several small chunks of free time. Even if I did have the time it feels kind of isolated being off on my own compared to sitting next to my family on the couch. On the other hand, sometimes I like being alone for a while, but the PC needs to stay in a common area where everyone can use it if they need to. Plus I have to be able to stop everything at a moment's notice to go be a dad. And I often play games in other places than my home. And I've always had an affinity for portables even when I was more into console/PC gaming. And a computer chair will never be as comfortable as a couch, bed, recliner, etc. And I have this weird preference for carts over disks (and especially over digital)...
Having a portable system solves all these problems without having to rearrange any other part of my life or home. Sure, the games look, sound, and run better on PC, but when you take all this stuff into consideration they're actually less fun to play on PC for me, and I'd have a lot less time to play them. I like the Switch a lot, but more than that it's benefiting from being the only game in town when it comes to portables. The Vita and 3DS are both great too, as are the other portables I've ended up with over the years, but they're functionally dead at this point.
So there you go. That's why I want all my games on Switch now!