[spankalee]

Well, crosswalks shouldn't have buttons. Pedestrians shouldn't have the burden of pressing the button in time to cross on the current signal.

[tokyodude]

Some signals actually do look at the crosswalk buttons. If no one is waiting to cross they keep the lights green in the direction of the most traffic.

[sp332]

That probably works for crosswalks at intersections, but there are other crosswalks with lights. I found a really nice one that turns the lights yellow as soon as you push the button.