Does that work with a touchpad? Does that mean switching to a new, unfamiliar mouse?

Look, it's a niche app. It won't make a billion dollars. It solves a small problem that some people have.

If you do some geeky "I can solve that problem for less", fine. But not everyone has brilliant problem solving skills, and the time to look at every alternative. They find something that works OK, and use it.

Some people use dropbox, not rsync. Programmers pay for Github, not a commodity host with git. Slightly suboptimal (from my perspective) products still sell, every day.

Yes, the Logitech MX518 for example. Above and below the wheel buttons to change sensitivity. Costs about 20€. Does not come in shiny white and it has an utterly confusing amount of buttons. ;-)

Yea... because that's easier and cheaper than downloading an app.