Why does Dropbox always make a .zip file when downloading?

Why does Dropbox make a .zip file when downloading jpg images? Jpgs are already compressed so zipping them when downloading only serves to create an extra step. When I used to send print jobs via Dropbox I always uploaded a .zip archive so fonts, mac postscript particularly, did not lose there resource info. Using dropbox to share images takes more time and steps because of this .zip process.

Is there a way to turn that off and download jpgs are is that the way Dropbox always works?

 

I use a browser, not going to use an app that can change preferences on my computer.

 

Thanks