Hopefully, people have other interests besides WoW. Many of us are nerds, whether it be movies, TV, books, or cartoons. Some people refuse to log on during their favorite TV show or miss a night to see a movie premiere or have to finish reading their favorite author's new book. These other forms of entertainment outweigh WoW in terms of importance to some people. Others just log on WoW and catch up on other media when the servers are down or they are bored with lack of new content.
I do not log on Sunday nights, mostly because I am watching Boardwalk Empire and The Walking Dead. Sure, I could record these programs and watch them later so I could maybe get in an alt run Sunday night -- but besides these being something I enjoy, I also take Sunday as a break night. One of my friends is an avid follower of a band (I don't really remember the name; they are pretty underground), and every time they have a show close by, he goes out of his way to see it. Another guildie announced that he would not raid one night because he was going to the midnight showing of the latest Harry Potter movie with his girlfriend; he claimed it was her idea, although I have my doubts.
So are there certain things you will not miss even to play WoW? Do you schedule your raiding or PvP nights around your favorite TV programs or new movies? Or do you just log on and figure you can always see whatever it is later?