My mom and her illustrators (chosen by her publishers) do events together, signings, receiving awards, and even some negotiations with agents and publishers.
And I'm not totally convinced it's such a bad thing for an illustrator to be chosen without the author's input or approval or anything.
I've noticed that authors seem stuck on getting "their" vision of the story captured. The thing is, then you're just sort of rehashing your own thoughts. Booooring. I've seen MUCH more amazing results (seriously, taking a book from "good" to "best seller") if the illustrator has their own ideas. Usually, if it's a big, successful publisher, they will do a great job pairing illustrators and authors. The writer and illustrator will share common ideas, but will take things in markedly different directions.
If your illustrator just sees what you see, you don't add any dimension to your story; you're just adding another flat layer. Sure, it can go awry, but most of the time, I think authors need to get over themselves and realize it's better to have a new voice telling the story rather than just an echo.