Agreed. It is the sellers responsibility to make sure the item arrives. Simply proving the item was shipped does nothing, because it may not have been received. If the seller can prove the item has been received, they are in the clear.
The item could be damaged due to poor packaging, which should not mean it's the buyer's fault for not wanting insurance. The item could have gotten lost due to going with the cheapest shipping option, which also should not mean it's the buyer's fault.
Whenever I ship anything out, on $50+ items, I always insure. When it's less than that, I still got delivery confirmation.
The buyer's responsibility is to pay, seller's responsibility to get it safely to the buyer.
I do always chuckle at the sellers who stress insurance is the buyer's choice... because it is not and PayPal/EBay will side with the buyer every time.