Some planes show so much adverse yaw with aileron that if you don't use the rudder to coordinate, you basically can't turn them. Cubs that are very true-to-scale are sometimes like that, I have a Tiger Moth that is close, and I flew a friends Yard Stick plane where full aileron with no rudder did almost nothing.

Of course you can do a lot with a computer radio and aileron differential to "fix" this kind of tendancy, but sometimes a plane's "bad habbits" are half the fun, espeically when they match the full-scale somewhat.

Plenty of planes fly just fine with just aileron-elevator-throttle though.

I agree that using a mix to avoid using the rudder in a turn is a bad idea. Using a mix to counter control coupling in an aerobatic plane is fine, but that's totally different.