Dogs are also for bucking. They work very well for that.
They simply provide leverage so that your arms get a bit of a break. If you're bucking a medium sized log, there are times where you should be using your dogs and times where you should be away/uphill as far as possible from the log making a point to not use your dogs/but the end of your bar.
True, you can over utilize this leverage by pushing on the handle and bog your saw down.
True, there are times where you don't want to dog the saw in cause you're worried about a pinched bar so you float the bar back and forth and watch the kerf carefully.
Longer dogs are primarily for thicker bark and/or larger diameters. General rule; most hardwood species do not need the bigger dogs.