Might not apply to most people, but on some of my machines I have left the mail app unconfigured and so the few times something uses a mail link launching the app will just land me on the setup screen. It’s rare enough that anyone uses those sort of mailto: links that I haven’t bothered doing anything about it. And it might be that most other people have their email program set up already so only me and a handful of others run into any sort of issue with that :p