Why do you think so? Rendezvous is an entertaining read, but I would never have thought of it as particularly “significant.”
I assume that’s a 
I believe they didn’t add too many recent novels because it takes time to see if something is going to be an influence. Some of the New Wave SF novels of the 60s were thought to be major works at the time, but I doubt anyone is still impressed by something like Bug Jack Barron any more.
You’re wrong, RealityChuck. I like Bug Jack Barron.
The Brits really invented the New Wave, but there never was any big iconic novel associated with the movement. It was almost entirely a short story genre. I doubt if Aldiss’ Barefoot in the Head ever made a splash on the SFBC. Probably A Clockwork Orange didn’t either, even if you can somehow put Burgess into the New Wave.
John Brunner’s Stand on Zanzibar is as close as the list gets. But that was 1968 and the world had changed a lot by then. Both Zelazny’s Lord of Light and the first Dangerous Visions anthology preceded it by a year.
I tried rereading Bug Jack Barron not that many years ago and I couldn’t get through it. But I bet I’d have trouble with The Moon is a Harsh Mistress too. :rolleyes:
I’m not sure why Dhalgren is on there. I read it, and it seemed to be nothing more than a somewhat atmospheric and surreal collection of generally repulsive sex scenes (some of which might be considered child pornography). The only thing that stuck with me was the character who said he would only give oral sex to men who had recently fucked a black woman with the clap, because he was some kind of dick conoisseur. What the hell???