Wearing a ring on your middle finger symbolizes balance and responsibility and is associated with Saturn.
Some people wear a ring on their middle finger so they do not confuse people on whether they're engaged or married.
People do wear rings even when they're not engaged or married and it's perfectly fine to wear it on the wedding finger however when you wear the ring on the middle finger it helps with confusion.
But sometimes people will wear a wedding ring on their middle finger and that is okay too as it really doesn't matter which fingers you wear the wedding ring on when married.
Sometimes for married people the wearing of the wedding ring on the middle finger symbolizes the status of a married relationship.