Given how successful they've been at that, I'm curious why you seem to view that as an aspersion on them rather than something to learn from? Shouldn't that tell us something about deploying internet-scale services?

(and, to be clear, the answer is yes, namely that a custom protocol has to deliver a lot of value to make up for having to deal with the deployment headaches inherent to anything less supported by firewalls, NAT boxes, etc. than HTTP/HTTPS)