I guess you may have a different viewpoint on this. But from my perspective, that's a context switch, I have to now load up my mail client and be subjected to whatever email arrived since I last opened it.

I also don't have "mailto:" hooked up to my actual email client, so that's extra steps for me to get that set up. (Blame me for this if you want to, but I'm guessing that there are probably more people like me in the world than there are people who have their email client set up to handle "mailto:" simply due to the fact that work is required to set it to anything other than the system default.)

The question is, what are you filtering for? There are always tradeoffs, and I hope I've demonstrated that the email-based interface is not "free" even for fairly savvy tech users. For less savvy tech users, I'd consider the situation even more difficult.