In my experience, most bar-fights (or any indoor fights!) start when someone is in-ya-face.
Muggings, by the time you realise wtf's happening, start IYF.
General street rumbles (multiple opp) start a step or two back, then very quickly progress to one or two people IYF.
Whether you think of yourself as a grappler/stiker/both, most of the time the range closes very quickly to IYF.
Is there any point in doing one-step sparring drills, where your opp starts one step back, and steps in with one/two/many attacks? Surely straight to IYF drills would be a more effective way of training?