I also agree with you for what it's worth. Even it is somewhat possible, it should be WAY more open and free. Like SSL it's not a luxury competitve edge, but basic modern day infrastructure
But they're not convenient for businesses : either they buy certificates for their employees, or they have them signed by the IT department, that provisions their key into any piece of corporate equipment.
Few companies are into the community initiatives, especially when it comes to security.
Also, CACert is not widely recognized. The root certificate is only included in a handful of Linux distros (like Arch or Mandriva, but not Debian)