Growing up my bed was right on the outside wall, my room had two outside walls and was cooler than the rest of the house but I was fine.
I had the outside wall half of the room when I had a roommate in college, my bed was right up against the bricks and windows. When we lived in an apartment we had our bed on the inside/shared wall and that just was not cool in an apartment, unless you just LIKE listening to your neighbors as you try to sleep. The head of my bed now is on an outside wall, and the side is about a foot from the outside wall.
Heck how can the bed not be on an outside wall?
Seriously, bedrooms are usually on the back or outlaying sides of the house, so the door is on the inner-most part of the room and the exterior walls are the logical places to put the bed.