What is the point?

I ask you ladies and gentleman what is the point of Flak Jacket? I have just started using it to get it pro... (finally got it pro) and RC cars still kill me.... You would think that a perk that protects you from explosives would protect you from a 2/3 killstreak. I'm just confused does flak jacket actually protect you from anything?

I'm not mad just curious as to whats the point. All my friends were always talking about flak jacket and how great it is but I still die by toy cars. any tips, I tried jumping but I still died...