Why does an explorer’s pack come with more things that can fit in it?

The Explorer’s pack comes with a backpack and a bunch of stuff that (I assume) goes inside.

A Backpack can fit 30lbs in it. But the stuff – a bedroll (7), a mess kit (1), a tinderbox (1), 10 torches (10), 10 days of rations (20), and a waterskin (5) – totals 44lbs.

My party holds the weight of stuff a bit loosely, rather than playing RAW. But if you did play RAW, you wouldn’t be able to carry all the stuff you’re given. Why would the game designers do that?