Why do staircases always have an odd number of steps?

Staircase have odd number of steps to prevent people from stumbling. Most people are right handed, so they naturally step with right foot first. And if the top stair will be an even stair then the person will be in it's left foot. But the brain is used to of right foot first, so the odd step will put them back on right foot, and there is less of a chance that a person might stumble.

Hence the Staircase have odd number of steps.