If those companies are like the one I worked for, they likely outsource their packaging production. The company that makes boxes for tampons might also make boxes for pizza restaurants, certain cleaning tools, cookies, baby food, etc.
The vendors that my previous company purchased from were cheeky buggers. One of our products that was only sold to retailers included a display shelf. These things used to be pretty sturdy. Now, they collapse under less than half of the weight that they used to have. The vendor denied it vehemently, and I think they are still lying about it to this day.
This particular vendor has a HUGE monopoly on cardboard, so it would be difficult for them to find another process suddenly. I hope they do, but who knows. They might hypothetically have a contract that they can’t break for another number of years. Yay.
I’m not saying any of this to say that it’s ok or good, but a lot of people can’t see what’s happening inside these manufacturing facilities. A lot of this is hush hush.