Soft Pedal on Upright Pianos

I have a question concerning soft pedal (also known as una corda) in upright and grand pianos. In a grand the soft pedal works by shifting the keybord to the side, therefore, the hammers only hit one string. In an upright, the soft pedal brings the hammer closer to the strings, and therefore changes the sound. My question is why cant the soft pedal in an upright work just like the soft pedal in a grand?

Thanks

Ben

That Is a very good question
I am not sure but I am 90% right in a upright piano they are a little bit shorter than a grand (shorter as in the width)
therefor there is not enough room to have the keys shift
also becuse the action is a differnt type

It'd be nice wouldn't it? I actually don't know why they wouldn't do that. I imagine so it makes the people playing grand piano's more Superior maybe? I honestly hope there is a good answer since I think it'd be aweful to not give it to everyone if they could.