Professor Bainbridge writes,

There is one governance problem that vexes me, however; namely, why are Subway stores owned by franchisees, while Starbucks stores are owned by the corporation.

Starbucks has an unusual real estate strategy that involves "flooding the zone." They are willing to have several stores near one another. That is the opposite of traditional franchise fast food, in which territory is carefully carved up.

The theory of "flood the zone" is that it is better for the corporation to have a lot of franchises in one territory, even though they appear to compete with one another. You need a corporate ownership to implement such a strategy--you could never convince individual franchise owners to do it.