Every sport was available live on internet feeds, and NBC's cable networks carried a lot of these sports both live and tape-delayed.
The prime time broadcast was tailored for the prime-time audience, not the sports junkies who knew how to find and use the live feeds. I saw (well, kind of... it was over 3G) the women's gymnastics team finals live, half a day before it aired on NBC primetime, using NBC's own iPhone app.
Thanks for your reply, but some of us work and can’t get the live feeds during the day. Still don’t see why NBC just chose to show boring basketball, volleyball, and boxing at night primarily.