I've been selling on eBay for 20+ years and have only ever used Royal Mail. I have never had an item lost in the post, or had a Buyer claim non-delivery, so why would I bother with coverage for loss? 

Also, I sell a lot of crystal glasses and have never had a breakage in transit via the Royal Mail. I have seen non-Royal Mail couriers throwing parcels around and mixing lightweight parcels with much heavier items (such as car exhausts etc), I dread to think how many breakages I would have had if I had used someone like EVRI. 

When considering the relative 'benefits' of a delivery method you need to take account of what you're selling and who you're selling to - eBay Simple Delivery  does neither of these things.

Simple Delivery is an overreach by eBay and I wonder what the motivation for it is. Certainly it doesn't benefit the Seller and in many cases it does't benefit the Buyer either. Commission from the shipping companies for eBay, perhaps?