In the real world no body is going to take off like that in combat because it bleeds of energy so unless your engine is providing very good tw you'd be fool to take off like that and bleed energy by the time you reach some altitude the bandit may already have you locked up on his radar.I have seen ADA take off which are the most quick take offs of our F16's.They are tasked to take off within few minutes if enemy is too close to border and they always take off through conventional method.
You might think a short take off to vertical climb is showing off but it can have uses in wartime.
For example, what if you don't have enough runway to do a regular takeoff because it's been bombed and you have to take off from a highway and there are obstacles such as trees and buildings?