There are two kinds of acts that make the R&R HOF list: (1) The early acts that everyone would insist on (BB King, Elvis, The Beatles, Chubby Checker, the Rolling Stones) and therefore lends 'legitimacy' to their other choices; (2) The acts that meet their standards of political correctness and they would like to construe as the legitimate successors of acts in the first group, even if they just weren't that popular.
The result is that Patti Smith, John Mellencamp, and Cat Stevens are shoe-ins because they fit the political ideals of the people running the group, just as Iggy Pop and Jackson Browne have before. If they could find another way to cannonize John Lennon, they would. (e.g., "We know we've already inducted him twice, but this year we are inducting the letter 'I' from the song 'Imagine'). Green Day can pencil their name in on the 2015 induction list right now.
In the meantime, they will ignore bands that were tremendously popular but largely apolitical, like Van Halen, Lynyrd Skynyrd, Rush, and Heart. And they will pretend that bands which espoused conservative or traditional values, like Kansas or Styx, were a stain on the very fabric of Rock 'n Roll.
Interestingly enough, since they the arbiters of 'taste' took over the playlists of Rock 'n Roll stations in the early 1990s and foisted an endless series of one-hit wonder grunge and 'alt' bands on us, the public has stopped listening to new rock 'n roll. The music formats that are now successful are Classic Rock (which plays Van Halen, Skynyrd, Heart, Rush, Kansas & Styx), and Country (which now sounds remarkably like mainstream rock from the 70s and 80s).
Oh well, that's enough a rant.
Which is why I was shocked Bob Seger and AC/DC were inducted.