Years and years and years ago, when I lived in CA, I used to purchase via the Internet from an outfit in Northern California. (That has long since closed and the owner has passed away). I loved this place, lots of variety and she carried everything. All items arrived bagged in heavy duty plastic bags stapled shut.
When I started my own little retail store, I contacted Gwen and made arrangements to purchase Wholesale from her and as I worked not far from her warehouse I also made arrangements to pick my orders up.
Imagine my surprise when I arrived at her warehouse for the first time, to be greeted by 3 adult Macaws, 2 Cockatoos and an african Grey all flying loose. In the center of the building were large tables and employees unpacking boxes of merchandise, sticking the merchandise in bags and stapling them shut. All the while 1 or more of the resident flock would be climbing in and out of the boxes or across the merchandise scattered on the table....
Needless to say I severed my business relationship with Bird Things, although Gwen and I remained friends until her death. However, I continually told her that I did not approve of her business methods.
Thus, for me, plastic bags just aren't enough. I do not want my birds exposed to your birds and your birds should not be exposed to my birds. IMO.
Maybe I am paranoid, however, I have had birds for over 30 years, I have worked as an Avian Vet Tech, I bred/raised birds for over 20 years, and have run a retail bird supply for over 10 years. In all that time I have *never* had a sick bird, not once, not ever.
I maintained a closed aviary and I currently maintain a *closed* shop for the protection of my birds and yours.