Practicality isn't the point (plus I may get better with practice). I play FPSs on my Pandora with the built in gaming controls often enough, and that is a very poor choice, as well.You should not expect to be able to use it in games.
Recently, I played Kaboom on my Atari 800XL with a paddle. The precision you need is not doable with a volume wheel. From min to max, on the Atari, there are 229 values. You can not get this resolution with such a tiny wheel.
Like levi said, it is mainly a "because I/we can" thing.