Hi! Maintainer of Pelias here and co-founder of Geocode Earth where we continue to fund Pelias development through our SaaS and consulting.

You need to bring Who's on First data in to support administrative areas, it won't use admin areas from OSM. This is a bit of a technical choice (WOF has some nice features like stable IDs and a rich hierarchy, and a data format that's much easier to work with), but also the result of the Who's on First project and Pelias being developed together while we were at Mapzen.

Don't hesitate to reach out to us if you need help getting things set up.