When a store has double doors why do they only let you use one of them?

Question

When a store has double doors why do they only let you use one of them?

Answer 1

maybe if the always used one breaks at least there will be another. (i dout it but it makes sence)

Answer 2

i have no clue problaby because they dont like getting too much air in their stores and stuff.

Answer 3

the other one that you don't use is for out

Answer 4

i dont kno, buh that is really wierd.