Honestly, I have a slightly different answer than most; because there shouldn't be. Docker already goes through great pains to achieve much of what it can do,

Honestly, I have a slightly different answer than most; because there shouldn't be. Docker already goes through great pains to achieve much of what it can do, and it would be bizarre to go through the effort to use it and then not take advantage of some of the core things it can enable. Even without Docker, service managers like systemd can be used to implement zero downtime deployments too. At this point it'd feel weird and broken if a service management tool just had no support for a "gapless" deployment. I'd feel uneasy using it. The way I see it, what Kubernetes does with health and liveness checks is actually just good hygiene irrespective of how many requests you can tolerate dropping, or if your container even serves requests to begin with. Tools that manage services should strive to provide similar functionality where possible.