First, you don't need to have an admin on the chain if you don't want to – the user who created the chain can remove their own admin permissions, then there will be no admin at all.
Second, you can easily set up multiple administrators if you like, then they govern the chain by consensus in accordance with the admin-consensus-* blockchain parameters. So it's possible for all the permissioned participants in a chain to govern it democratically rather than having a central admin.
Third, the purpose of the admin or admins is to allow other users' permissions to be changed, install/approve transaction filters, and upgrade the blockchain parameters.