I buy stuff all the time from various retailers that ship stuff via USPS priority mail - Todds Models, Dreamworks, Tower Hobby, Troybuilt, etc.

I do not recall specifically being offered to purchase insurance during checkout by any of them. Nor do I recall any of them informing me that I was assuming risk of loss or damage. I have always assumed that they bore the risk until it gets to my door.

I am not saying I was right to make that assumption, but that is what I assumed.