I can really only speak to CloudFlare workers in latency sensitive, user-facing settings, but from my experience their cold start times are insanely low, like 5

I can really only speak to CloudFlare workers in latency sensitive, user-facing settings, but from my experience their cold start times are insanely low, like 5-10ms. They use V8 Isolates (uberjar for js?) running WASM bytecode, so there is very little runtime overhead. So in that case, there is an actual benefit that being a short hop away, but otherwise I think you're right. I've also used some AWS Lambdas and GCP Cloud Functions in background data processing settings where there are under 1M invocations/month, so its cheaper than running a tiny instance 24/7. In that setting latency doesn't really matter as much, but I was seeing cold starts ~2 seconds and warm start invocations on my node and python code responding within 30-60ms in most cases. Once the container is up and running its reused for follow-on invocations, but eventually(and opaquely) times out and the next invocation will be cold. People who are using serverless runtimes have historically done hacky things to ensure they always have a running container like invoking the function with a cron job. At that point it seems a bit silly not to just run a small vm / container.