To implement that many clients run as a root. Even if that root is in a docket container, this is needlessly elevated privileges especially given the complexity (again, needless) of many clients.
The sad part is that it is trivial to run most of the clients with an account with no privileges that can access very few files and use a unix socket to tell the web server to reload the certificate. But this is not done.
And then ideally at this point the web servers should if not implement then at least facilitate ACME protocol implementations, like, for example, redirect traffic requests from acme servers to another port with one-liner in config. But this is not the case.
