Personally, I find it handy to have the autoattack button.
You both mentioned already hunters use it more than other classes I think.
At some fights, like final boss in Dark Delvings, you have to stop attacking for a while since he reflects damage for some time. As melee class, you can run back, but as ranged, you should stop the autoattack. You can do that by not selecting the boss, but I prefer to have him still selected and to see the buff. That way I can immediately start attacking when the buff expires.
Just a matter of preference I think ;-)