Why is the Windows Store app install so big?

I recently made a game for android and windows store. android apk is 25mb, windows store is 30 mb.
But when i install the windows store app to WP8.1 mobile (Lumia 430), it shows that the install size is 427MB. Woah, Why so big? and what can i do to reduce the size?

Using Unity 5.3.5p1.

I’m not sure what is going on, but the .appx file that is created is a zip file. If you rename it to .zip it’s easy to open up and see what is inside. Maybe that’ll help find a way to reduce the size.

It was really stupid of me. I had selected the same texture compression method for all my build types. I was using 16 bit compression for all, android, windows, standalone.
It does have a small size for android, but like i said windows size was huge.

I have now selected the crunched method for windows. shared assets size down from 395mb to 33mb.