Portability.
I find that a lot of games that I want to play these days are not necessarily the best lookers on the market. Even if they are astounding visually, I'm willing to put up with some sacrifices in order for it to be on the go.
The reality is, as I get older, the opportunities that have been available to me to game comfortably have become less and less. Just having the chance to take something on the go has substantially helped improve the opportunities and chances I have to play games.
What's more, a lot of the games that I still love to play - a combination of JRPGs, WRPGs, and short, burst-like game sessions with multiplayer titles like Splatoon and Arms - fit the nature of the portable console.
It's why the Switch remains such a powerhouse console for me and my personal gaming habits.