Lots of excellent responses in this thread, and I agree with all of them.
Just to add one more point: normally the Church (and therefore the faithful) require a MIRACLE to prove that a message is from heaven. No miracle, no locution.
Our Lady of Guadalupe: Bishop said, "Where's the miracle?" Our Lady produced flowers out of season and the miraculous image.
Our Lady of Lourdes: Dig in the dirt, and a spring will come out that will cure people.
Our Lady of Fatima: "Tell everyone to come to this place on October 13th and they will see a miracle." Well, they sure did.
Our Lady of La Salette: Was not approved until people were miraculously cured on the site.
I don't know of any vision from heaven that has ever been approved without miracles taking place there.
So ... where's these people's miracle??!
Another good point.
Keep in mind, asking for a miracle from God (or Our Lady) during an apparition, especially if you are expected to write down/publish said apparition, is like asking you for a penny. NOT A BIG DEAL. It's a big deal to US, yes -- but not a big deal for God.
It would be like trying to pick up someone's kids at school, and not bothering to give the "code word" (to show you're legit sent by their parents to pick them up) -- when you HAVE the code word. I mean, the kids are TRAINED not to go with strangers unless they give the prearranged code word, and you HAVE the code word, so ... what's the problem?
Miracles are like Heaven's "code word" to help us distinguish between true (rare) heavenly messages, and the devil's deceits.
Also, Protip: God will not be the least bit upset if you totally dismiss an apparition that seems suspicious to you. It's what we're supposed to do, it's what the Church teaches about private revelations and apparitions. We are supposed to be skeptical by default. Remember, we don't need ANY of these revelations to save our souls.
The fact that Our Lady deigned to procure miracles at Fatima, Guadalupe, etc. shows that she has no problem with the skeptical bishops -- and went out of her way to accommodate them.
She approved of their skepticism!