Not an electrical engineer, but here is my take:

HID headlights need to "charge up" before it can illuminate at its full potential. Hence when you turn your fancy HID headlights on, there is about a 1/2-second or 2-second delay before the lights actually light up -- the light looks a little dimmer during that delay/charge up period.

Halogens don't have that problem. With that, it makes very little sense to have HID high beams; a lot of times people only use the high beams to flash. In other words, HID high beams won't flash properly.

 

I thought the 7 series had HIDs prior to '96........ and Mk VIII was first US made car to have HIDs....

Gotta look that up somewhere.

Edit: according to the Sylvania website, you're right. '95 Mark VIII was the first car in the US market to offer HIDs.

http://www.sylvania.com/ConsumerProducts/A...ntQuestions.htm

 

i might be wrong about this but i was under the impression that the merc. SL had hid high beams as well. Guess i'm gonna have to do a little searching.