When I bought my Saleya MM (AT LV!!!) the lady took off all the plastic (the bubbles inside, and the blue stuff covering the zipper pulls) and took the cardboard out. I asked her if she could keep it there (just because I wasn't sure if I was going to keep it or return it, and I wanted to keep it perfect.) She said that they HAVE to take it all away. Perhaps some LV boutiques let you keep it in, I don't know. Just relaying my experience.
Nah. I buy from LV all the time and if you request that they keep orignal packaging on they will. Maybe it just depends on the relationship that you have with your SA.
I bought a mono Mizi before they were discontinued and asked the SA to leave the plastic on the handles and she did. No probs.
I also have a Denim baggy that cam with plastic on the handles and the buckles.
The SA that you had was just being difficult. Lots of ladies here have bought LV with original packaging on it. Its not that big of a deal for them to leave it on.