Meh. Simply making the default pool larger would go a long way towards moving systems out of a desperate situation. With that done there would be a lot less reason to short circuit it and go RdRand only.
No one is concerned about RdRand as a contributing source— with other genuine source of randomness RdRand isn't likely a back door once mixed in.
Making the pool larger isn't sufficient for embedded systems that don't have a lot of sources of entropy in the first place. Especially since very often the most critical secrets (such as the RSA keys for the certificates used by network printers, for example) are generated when the embedded system is first installed, where even if you have a larger pool, there isn't any opportunity to fill with the extremely limited amount of entropy available to said device.
As in your example, the only source of entropy a network printer has: network data, easy to manipulate or even no activity. So no way to generate keys for example.
In some cases hardware sources are a must. Yes, in the end you'll need to trust them
No one is concerned about RdRand as a contributing source— with other genuine source of randomness RdRand isn't likely a back door once mixed in.