As the author of Caddy, I have often wondered why people run it in containers. The feedback I keep hearing is basically workflow/ecosystem lock-in. Everything else uses containers, so the stuff that doesn't need containers needs them now, too.
Having said that, for serious business, this setup doesn't make sense. It possibly takes more work to operate as container when the gateway runs on a dedicated instance.
Of course there's also the well-known correlation between the quality of your k8s deployment and the number of proxies it hosts. /s