And I agree with you that the instant retaliation is tiresome and unneccesary. However, with competent officials the aggressor who attacks the hitter a lot of times is receiving the instigator or extra minor penalty resulting in a power play, so while it is annoying the rules still usually get properly enforced.
There are a lot of instances where NFL players get into it in similar skirmish's, and perhaps we'd see it just as frequently if the rules weren't as harsh. Any punch thrown is an automatic ejection + fine and possible suspension. If the NHL had the same enforcement the fighting would be gone, however you'd have the Matt Cooke's and Steve Downie's of the world causing havoc. Kind of a catch 22