It's clear enough from this Q&A and the null output from cat /sys/power/state that the Raspberry Pi does not currently support the Linux kernel's Power Management features. This explains why there is no sleep mode for the RPi. As RPi production numbers may now be in the range of one million units/month, I find this a little surprising, and so I'm posting this question in an effort to learn whether RPi's lack of support for Power Management is due to:
RPi hardware simply lacks the capability, or
It's not a development priority
I realize this may be asking for an opinion instead of an answer. If it is, it should probably be closed. The second question may well be subjective - unless The Foundation has publicly announced their objectives. But I'm hopeful that the first question can be answered more objectively - if not definitively - by those more familiar with the ARM technology and architecture used in the RPi.
