The usability of window blinds

The other day I was watching Family Guy’s latest episode (“12 and a Half Angry Men”). This funny scene inspired the post.

Peter struggling with the window blinds

Peter struggling with the window blinds

Well I guess the animation says it all. To open/close the blinds you’re supposed to alternately pull on the two strings. Although I knew the theory I could never do it in practice – one of the sides was always lower than the other (that’s not an april fools joke – I really can’t operate those things). Clearly no one wants to have the left part all the way up and the right – halfway down, so why was it designed this way?

Why couldn’t there just be a single string doing all the work or one for opening and one for closing?