"You don't need Kubernetes, for a Linux user you can already build a custom solution quite trivially by setting up a custom package repo then build and distribute your application using apt, then configuring SysVinit to monitor your services, whilst using Ansible to configure iptables rules in combination with a simple load balancer you can manage yourself, then use syslog to monitor logs across all your machines whilst hand-waving away secrets management as a problem with 'serverless'"

Yes, you could. Some people do. Others don't, because even if you need a small portion of the features a turnkey solution is likely a better choice in the long run than hand-rolling your own mix of 15+ different technologies to achieve the same thing.