Prop pitch controls aren't always rigged perfectly. In fact I find it's better to get into reverse gently rather than slamming them all the way to full reverse. Particularly if you fly a fleet of airplanes. With that said, I find fine steering with differential beta or reverse on runways or taxiways mighty convenient in a twin turboprop like a King Air. Not really necessary per se, but convenient. But if you're pulling a whole bunch more reverse on one side than the other, I could see it leading to control problems!