Reverse and drive off? You're in a car...
Same with these groups of people, honestly a single guy with a knife is going to struggle to take on 3 average sized guys if they all approach with intent and encircle...
That's a nice plan but only trained personal like off duty police officers or ex-forces would likely do that, most people are flighters not fighters.
They don't know if the attackers have guns or explosives on hand either.