This why in a lot of contexts it would be good to at least be micro catching them.
If they were cached for 5 seconds it would have covered all subsequent requests.
404s have got to be very cheap to serve
But they aren't always!
Not when you're on a metered connection, or on a high latency one.
Don't make your customers pay for your sloppy habits is a good policy to have.
If the CDN returns a 404 or the origin server, then your satellite phone is still waiting.