Parish Boundaries

Has anyone other than me wondered why Mill-on-the-Mole is in Bishops Nympton parish?

I know that historically the parish boundary on that side of town is the River Mole, but I doubt whether many of the Mill-on-the-Mole residents ever go to Bishops Nympton.

Why would they? After all, the facilities they use are literally just up the road in South Molton.