sending zipped photos

I just sent somebody some photos they had lost , the photos totalled 15mb so I zipped the folder. I expected zipped to make the folder smaller because they are compressed but zipped and unzipped were the same mb size so what is the point of zipping them ?
 
Solution
Jpeg images are already compressed. So archiving them doesn't give you any significant space savings.
If you tried to compress any non-compressed image formats like bmp, then you'd see a significant difference.