Tyvek is loud. I used it to sew furniture covers for a cabin that is left unoccupied in winter. Shaking out the bed covers to put them on is deafening. Walking with a Tyvek pack might drive you mad.

Those IKEA bags are pretty freakin loud too. Both are materials I wouldn't want near me.

I don't think tyvek would be strong enough for a backpack. It is used a lot in backpacking for ground sheets and even shelters.

Tyvek also breaks down in UV light.