> I must admit I'm hard pressed to come up with a use case for this. You could just as easily do a regular HTTP request on a separate thread and throw away the result to get "zero latency" fire-and-forget behavior.

I do this quite often, and creating another thread might be easy to code, but it's harder on capacity planning and management. It's also hard to gossip utilisation of a shared network link across a cluster, so e.g. if requests are infrequently sourced, I may want to permit a pool of 500k concurrent output HTTP requests across the entire cluster, but I don't want to give every machine a mere 10k outgoing since busy endpoints would be starved by unbusy ones (and my network link would have plenty of spare capacity). Managing all that could be a full time job if I went down the "easy" path of just creating another thread.

Using UDP means if there is network congestion, messages just get dropped and I don't waste more network and CPU traffic by sending retransmits. I have retries further up the chain anyway for other reasons, so it makes sense to me to have less code and reuse what I've already got.