As we try to get customer off on-premise servers, having DHCP and DNS hosted locally is key to making that occur.
Both the MX and MS devices can host DHCP server for local subnets, but public DNS servers are the only alternative in getting customers server-less and completely cloud-hosted.
Local DNS isn't as essential as DHCP, but makes local resources easier to manage on a client network - like printing. I've been able to use DNSmasq on other linux based routers/firewalls to accomplish this. It would be nice if Meraki integrated a simple local DNS server option.