It's Vegas... The SAs expect tourists and some of them will leave happy with a bag, but the LV SAs also value their locals and frequent clients who make Las Vegas their home boutique.
While at the boutique, I have seen tourists walk in and *immediately* ask for a Kelly/Birkin with a look on their face that they are going to be ONE to "get the bag" that day. I have also seen polite visitors who truly seem to love H get offered bags and it's great to see.
It has been said often on these threads, but just be patient and polite, show that you are really knowledgeable about H/love the brand, and maybe things will work out for you that day. But don't take it personally if they say that there is no stock because sometimes there really isn't that much stock available.