Ignition Interlock

Riddle me this: A law is passing through California legislature requiring drunk-drivers to have ignition interlock devices fitted to their cars.  Ignition interlock is basically a breathalyzer that you have to pass before the ignition will work.  Sounds great to us squishies: drunks are left where they can't hurt and scare folks, and most of the time everyone in a group is drunk if the driver is so "Hey Fred, breathe into this" is a weak counter (and would attract bonus special sanctions).

Now, here's the thing: According to the article, ignition interlock appeared on the scene in 1987.  And the current law will only start a pilot in 2010 with California-wide coverage in 2016 assuming it isn't banjaxed by politics et al.

My question is this:  Why the hell aren't these mandatorily installed at the factory?  Why the hell haven't we got them over here?