Mobs don't drop loot

When i was trying to get some leather, from some cows there were no drops. No beef and no LEATHER. i killed like 12 cows before I realized this. so I tested it some more on some zombies, creepers, spiders, and skelingtons. but only the armor droped. I only had to test on them bc if they were not working the whole loot system was broke. 

   Mojang please fix this so I can have some leather and steak for Christmas.

   <3 Blue10power