I wasn't trying to imply that it was an issue of skill, just an issue of use. How much of the marketshare of an Android/iOS platform is going to see keyboard and mouse support, then decide if you even need to focus on that stuff.
I think there are now more people who own a keyboard for their Android, iOS, and Windows 10 smartphones and tablets because Bluetooth Keyboards are becoming more portable and affordable where a wireless Bluetooth keyboard for tablets and smartphones cost around $10 on eBay. There are also cheap $3 Micro-USB OTG cable with a full size USB port to use to connect a desktop USB Keyboard to some Android and Windows tablet, and most people own USB keyboards. There are probably many millions of people who own a Bluetooth keyboard which would work on a modern smartphone or tablet which usually has Bluetooth.
If the mobile game maker actively advertise or write a blog and forum post that their game will work on mobile devices with keyboards, the mobile game may get an extra few thousand or more keyboard gamers. Having a few thousand extra gamers is a decent amount of extra fans who will support your games.
The marketshare of physical Keyboard and Mouse users is smaller, but Keyboard and Mouse users maybe more loyal fans of a mobile game. Keyboard users maybe more willing to spend more real money on virtual items like virtual weapons, other item , DLC, and virtual money for buying in-game items in a game, and also support the makers of the games. Keyboard users may also have more money to spend on virtual items because they can afford a wireless keyboard, or bought a more expensive tablet like the iPad Pro, Android Pixel C, and Microsoft Surface Pro 3 where using a keyboard is an important part of using these tablets because they are designed to be laptop replacement tablets.
The mobile games industry is also very competitive, so having an extra few hundred or thousand mobile gamers who prefer keyboard and mouse may help make a mobile game slightly more popular, so the game maker earn slightly more money from ads, and in-app purchases to pay workers to add more features, levels, and characters to a game.
There are also a lot of disabled/handicapped people who may prefer using a mouse, and keyboard because of limited hand movement because of a injury or disability, so they maybe able to play mobile games if there are alternative ways to play the games with a keyboard and mouse, or controller which is designed for people who don't have fast finger and hand movements.