Random Attack

I think violence like that sucks ...
If someone's that desperate to have a fight, why not train and get it out in a ring or something, with like minded people that hit you back?

Cowardice, pure and simple. If you step into a ring it's about fairness, an even match, a contest, in a controlled environment. Those who want to 'deck' someone for kicks 9 times out of 10 will stack the odds in their favour (attacking from behind, having some equally vile mates lurking nearby, using a weapon, etc. etc.). People who carry out these sort of random attacks don't have the guts to do what you're suggesting.