In part because a large fraction are bullshit.

I have seen boxes with 'Open carefully, do not use a knife' on the outer box when there was another set of cardboard boxes inside protecting the product. Oh yeah, real glad I didn't cut the tape with my blade that's not long enough to fully cut even one layer of cardboard.

I have also seen a label "delicate product, fold carefully" on fucking denim jackets.

When everything is 'fragile' nothing is. If you won't pay for a packaging engineer then pay for actual special handling.