"hardware is quite reliable" is not a valid strategy. Hardware fails with some non-zero probability. You need to have a plan in place what to do if that happens, taking into account service disruption, backups etc.
Having a system in place that handles most of this gracefully (like kubernetes) is one way of having such a plan, there are others. Which one works best is dependent on your app, cost of downtime, your team that's tasked
with bringing everything back up in the middle if the night, etc.
People who leave details like this out when they say "kubernetes is complicated" just haven't seen the complexities of operating a service
well.
