The Username password functionality should be optional in Nano and Micro embedded profile, now that ECC security is required in these profiles. The requirement for some level of security is handled by ECC.
The correct use of Username/Password in a device requires an Random password be generated for all devices as they ship. It also requires an infrastructure for updating and managing password (complexity rule, repeat rules, timeouts etc). For a Nano/Micro class device this is just not reasonable. Also this class of device does not have User level interaction typically - so it does not make sense (they are just a sensor that transmits data). The only use case that could apply for an administrative user access, would be related to provisioning, but this can be handle in other manners. [Application Instance information]
If user access is required, then X.509 certificate makes more sense (these could also be managed by the GDS - and would require no additional externally define management).
[In the world of multi-vendor systems the management needs to be able to be centralized and User name Password does not fit this model)]

[This is a request from FLC]