K8S is basically another answer to Conway’s Law. Every startup I’ve worked at switched to it because then the infrastructure could map more closely to the code. Not unlike microservices at a higher level.
The old-skool approach is depending on a team of SREs or sysadmins to provision hardware for you and basically handle the deployment, which K8S plus container images basically abstract away.
Not to say that dedicating resources to platform development (k8s style) isn’t a time sink when you’re trying to build product and find a fit in the market.