Hiring is hard. Sure there may be a theoretical "better hire" outside of the Bay Area, but if they have someone in front of them who seems like they would do a great job and wants to work for them, it behooves them to hire that person now, even if it costs more. The cost of not hiring them is probably more, in lost time and productivity.

Maybe as they get bigger and each individual role becomes less critical, they can start to focus their recruiting on areas outside of SF. But right now, given that the founders are in SF, it's probably a lot easier to recruit people here.