While a static IP on your WAN is usually an extra charge and therefore not very common for most residential internet accounts, giving a device a static IP on your LAN is often necessary if port forwarding or other special services are needed. Assigning static, permanent, or a reserved IP is handled by the end user's router. For my SlingBox to stream over the internet requires that I forward all requests to service port 5001 to the SlingBox. The only way to do this automatically everytime the router/and or the Slingbox boots up is to assign it a STATIC IP on my LAN which I do using my router.
Giving the tech support person the benefit of the doubt perhaps something similar is required so you can access your Dish receiver from the WAN.