If your in manual, your thumb and that dial should be married. Seriously, one of the first things you gotta know about aperture is where to control the damn thing right? Before knowing where to change settings in my camera, it would take me some of the longest seconds ever (in my mind under the pressure) just to set up the proper aperture to get the whole group in focus. Not very fun for a working photographer. So that's pretty much mandatory. Yep, no excuses...
But What Does Aperture Do In The First Place?
When I first started, all I did was use it for letting in the most light possible. Shooting music performances in low light had to give me as much shutter speed as I can muster without it being to dark or to bright and off focus.