Question

Why does friction occurs when two surfaces are in contact

Answer 1

yes that's a very nice question and the answer is that because friction is a kind of force in which object gets heat and heat can only be formed with the help of two surface only

Answer 2

I think that every thing in this universe is a conservation means whole universe is a conservative field
nothing can be created nor destroyed
so when two surfaces are in contact to each other applied force is there to oppose applied force friction force created

hope it helps u