When the AFCI requirement first reared its head they were needed for "receptacle outlets". In fact, that's where the Chicago Code still is.
The next NEC Code cycle that was revised to specifically remove the word "receptacle" so that it would apply to all outlets; be they lights, receptacles, hard-wired, or whatever.
I was told that the bedroom receptacle outlets was indeed intended as a starting point. The eventual plan was to included everything in the entire house, but they wanted to start small to see if there were any major issues before they expanded the requirements.
