I find gamepads to be more comfortable than mouse and keyboard, and most modern games are designed such that all of their functions can be performed comfortably on controller. I also tend to play a lot of games that benefit from having an analog stick.
All just preference, of course. Kb/m and gamepads are good at different things.
I think that article's headline is incorrect. Valve's article said that 10% of controller sessions are Steam Decks, not 10% of Steam Input sessions. Here's Valve's article: https://steamcommunity.com/games/593110/announcements/detail/4142827237888316812
So weird that only 15% of Steam sessions are using controllers. I thought everyone had a controller. Most games are just better with a gamepad.
59% of controller sessions are using Xbox controllers. Not surprising, but I wonder how many of those Xbox controllers aren't actually Xbox controllers. I use an 8BitDo Pro 2, which uses X-Input on PC. Though the majority of my gaming is done on Deck now.