Most application I usually install (opam, cargo, vscode, julia, ...) keep a local storage in my home folder. Is there a reason for this preference? Or better, are there downsides to the alternatives?

For example sometimes it is suggested that such files should be located on /var, or in ~/.local/share, but there might be issues or annoyances in using these folder in "cross-distro" application.

Do you know any such possible issues?

[any answer o any of the three questions i asked here would be satisfactory]