From an article on OregonLive.com by David Greenwald on Grammy Winners and Losers:
"Lou Reed: Instead of the music of the late Velvet Underground frontman, truly one of the great influencers of and contributors to American popular music, the Grammys let Jared Leto give the rocker a short spoken tribute and had Reed's "Lulu" collaborators, Metallica, play their own staple hit "One" with classical pianist Lang Lang. Couldn't make room for Dave Grohl to do "Sweet Jane"? What a shame."
Apparently, the NARAS determined Lou didn't sell enough recordings to warrant true tribute to his Velvet Underground and solo careers.
Here's a link to the entire article by Greenwald: