As far as Australia Post is concerned, no-one mails letters anymore. Because of course, everyone wants to use an $8.25 prepaid satchel or a $9.10 BX1 box ($1.65 + $7.45 Parcel Post, not even counting the cost of bubble wrap) for a $4 DVD with free postage rather than putting two stamps on a large envelope or bubble mailer!
They might be correct about the decline in regular paper material being sent by mail (handwritten letters, birthday cards, printed material), but I'm sure sending large letters has increased tenfold over the years.
I'm also starting to think that the 151x229mm PB2 padded bag/bubble mailer size was deliberately chosen to be ever-so-slightly too small to fit a DVD* in order for people to use Parcel Post! Hence the widespread use of non-AP 160x230mm mailers (and yes, the bubble wrap lining does make a difference compared to plain paper and so-called "tough" bags, at least when it comes to sending flimsy old DVD cases, or worse, brittle CD cases which shatter like glass).
* Yes, you can fit a DVD/Blu-Ray case in a PB2 mailer, but it's a very tight fit and not recommended since you're just asking for the case to get crushed or cracked. That or the mailer will tear itself apart when trying to fit them in there, which I have had happen before.
