Here is a very nice analysis of Youtube videos of street fights by an assistant professor who is also an avid bjj enthusiast. Stats like “57% of the fighters who ended up on the ground were taken down by a throw, a trip or being pulled to the ground.” conclusions like “So learning how to grapple and more specifically; how to apply and stop takedowns is vital to fighting.” and general admonitions like “Do not be the first person to hit the ground!” are some reasons that give me a preference for arts that focus on balance, throws and takedowns (and hence defences and control of the clinch range). I think his study and conclusions point to this kind of need at least as much as the need for ground skills.