Did you ever see two nervous men trying to psych themselves up to fight? It gets a bit pushy-shovey until one of them finally throws a punch. They don't have the self-confidence to get things rolling.
A trained fighter would simply get into it and take his opponent out as cleanly as possible.
A snake knows what it can do, dispenses with the dance of engagement, and strikes. It's best not to annoy them if they're in a bad mood.