The simple answer is that a society cars are heavily prioritized and pedestrians and cyclists are not. So traffic engineers by default set crossing buttons to

The simple answer is that a society cars are heavily prioritized and pedestrians and cyclists are not. So traffic engineers by default set crossing buttons to have a delay so the poor motorists aren't somehow inconvenienced by a person wanting to cross. Note that I'm not referring to lights where pushing the button inserts a crosswalk cycle into the next light change. I'm talking about single street crossings where you push the button and nothing happens for anywhere from 30 seconds to minutes.