Because there have been other 'fads' still being strong today.
Kubernetes solves real problems which have been hard for a long time. Its the first thing you, as an infrastructure team, want to have to be able to provide your teams a manageable environment for yourself.
mesos, nomad, docker swarm and co.
Developers don't want a VM and you can't manage and maintain VMs if someone else is doing something with them.
Cloud native is here to stay; It will affect and already affects tools, applications and architecture.