Cows exit mine carts when you log back into the world.

Cows exit mine carts when you log back into the world.

What I expected to happen was...:
Cow(s)would stay in mine cart(s) when I leave the world.

What actually happened was...:
Cows exit mine carts.
Steps to Reproduce:
1. Place a cow into a mine cart.
2. Save and quit to title.
3. Re-enter the same world.