Even though PC gaming is more popular and better supported than ever, that are simply some games that just don't function well with a classic mouse & keyboard combo. For me the best example of this would be action-RPG games like Dark Souls or Monster Hunter: World, because while they may be fully playable with a mouse & keyboard, the experience is nowhere near ideal when compared to the flexibility you gain by using a controller.
It would appear that there are a lot of other PC gamers that share this sort of sentiment, because according to Valve's recent blog post on controller gaming on Steam, more than 30 million Steam users have a controller! What might come as an even bigger surprise is that 15 million of those players have more than one controller at their disposal, which to me indicates that there is a larger intersection between console and PC gaming than most would assume.
"Console controllers make up the bulk of devices, but the remaining 8% are significant, totaling nearly 5 million controllers," reads the blog post. "This is a group that consists of Steam Controllers, PC gamepads, Nintendo controllers, and fightsticks (and don't forget the 783 dancepads). This is a large, eclectic set of input devices that, in some cases, take quite a bit of user initiative to even connect to a PC."
Unsurprisingly, Xbox controllers are at the very forefront with 64% as they have enjoyed native support for many years now, whereas anyone attempting to use PlayStation controllers in the past few years would have also had to install an additional program in order to convert its input... not exactly ideal for casual gaming. What is a bit puzzling is that 20% of all Xbox controller owners used it at least once in the last month, whereas only 9% of PlayStation controller owners did the same. Whether this indicates something about the quality of the controllers and their user experience, I'm afraid the data simply isn't there, but it's certainly an interesting fact to speculate over.
So far the Xbox controllers reign supreme
"To date, we have sold 1.3 million Steam Controllers, but it's how they're being used that is most interesting to us," continues the blog post. "The Steam Controller community plays a more diverse selection of games than other controller types, interacting with nearly twice the total number of titles compared to the next closest device. Additionally, many of these are titles without built-in controller support."
In order to better support Steam Controllers, as well as "over 200 controller models", Valve will continue going all-out with Steam Input integration. As this is a native part of Steam, the support can easily be extended to new controllers without any effort from developers, meaning that if everything goes well, you will soon be able to completely stop stop worrying about which controllers are optimal and which are going to be a hassle to set up.
You can read more about Valve's plans, as well as check out some more stats, over at the official blog post. I fully recommend you give it a look as it really is fascinating stuff!