What some of the dudes who hate thinking about grappling and BJJ for the reason that "if there's more than one guy, it's all useless" fail to realize that learning the ground game also helps you have a better chance of getting off your back and right back on your feet. If the guy on the ground didn't have training in grappling, the guy on top would surely have total advantage.
It's stupid to pull guard if there are people around who may curb stomp you, so it's better to do something better on the clinch than pulling guard. Clinch grappling helps a lot in not only grappling or takedowns, but also striking (some sambo and wrestling dudes who did pro boxing supposedly said that it helped them a lot - Jack Dempsey is one such person).
So yeah to defend yourself well in both street and MMA, knowledge of three things would be advantageous: standup, clinch, and ground game. Or at least do well enough to avoid one in order to do the other.