Why doesn't Amy Poehler just stay on SNL?

She kept on appearing and surprising us on Weekend Update every so often last season after she left the show, and now she is doing Weekend Update Thursdays, and everyone loves her on there. I don't know why she can't just stay on. I heard Kristen Wiig is the co anchor this upcoming season with Seth. I like her too, but I don't think she will beat Amy on WU, plus I always liked it when she came on as Judy Grimes and she probably won't be able to do that anymore!