The Carters going to Taylor's bday bash was a spur of the moment thing, they had met at the Billboard event earlier in the day and Taylor must've invited them there. They prolly didn't have much to do that evening so they went to her party. It didn't require any prior planning or anything.
Kanye's wedding was in another country, plus Beyonce cleary doesn't want to associate with the Kardashian fam much anyways (I mean who can blame her?) so thats that.