Why is it wrong for a couple to sleep in the same bed without sex before marriage?

maybe because your parents think that it won't be just innocent falling asleep together and they don't want you fooling around in their house. they probably think that sleeping in the same bed is for couples who have had sex. and since your not married, sex is wrong in their opinion. it sounds way to strict and old fashioned to me, but just respect your parents wishes. when you're outside of their house you can do whatever you want.