You've gained that happening much less frequently. The tradeoff is making every other problem harder to diagnose.
Add an ephemeral container to an already running pod, for example to add debugging utilities without restarting the pod.
https://kubernetes.io/docs/reference/kubectl/generated/kubec...
And even that's only true if you assume kubernetes is the only place your container runs where you might want to also debug it.
For the rare cases where you find yourself needing to attach a debugger to your pods running in staging/prod, a debug container is absolutely the right tool to reach for.
How wasteful though? I have to admit, I envy the person whose codebase itself they have to support is so lean and space-conservative that the size of the gnu coreutils, curl, nano, etc., would show up as anything but a rounding error in the image size.
I see it like putting a thermometer in a turkey before I stick it in the oven. Sure, the thermometer adds thermal mass itself, making the turkey take a few seconds longer to cook, but the value of it being there is greater than the cost imposed.