If it can't find an LSP binary, Eglot will prompt you to pick one, and tell you which one it was looking for. That seems reasonable to me. I wouldn't want Emacs to download and install random binaries on my system automatically.

My experience with Emacs 30 is that Eglot will prompt and show nothing of meaningful assistance beyond a name. That leaves me to run a google search to find whatever binaries fit the description.

They host binaries already; why not host all of the binaries necessary for the supported features to function?