Low resolution photo stream?

I shot a bunch of photos on my iPhone on a recent trip. I was hoping that they would go over photo stream on my iPad where I could edit them in iPhoto and maybe share them. The problem is iPhoto is telling me that photo stream photos are downsized to 3.1 megapixels. What's the point of that?

according to Apple photo stream will "automatically upload new photos and send them to all of your iCloud devices when connected to wifi"

so if it only works over wifi then why not upload full size photos? If it uploaded over cellular then I can understand because some people have limited amount of data. Over wifi most people don't have that limitation. This just makes photo stream completely useless to me.