"Looks like the "obvious" thing to do would be to just opt for the so called CDMA2000 "3G" system"
That's what the consumers are doing, opting for the better system, 1X. Why are there two systems?...competition.
1X is 3G, you've questioned this many times and I've seen more than one poster post a link to this fact. But why would that matter, call it what you want, there's a reason KDDI signs up more customers in a month than NTT does in a year, one works and the other doesn't...and ultimately, 3X and HDR will be available if faster speeds are needed, and at low upgrade costs as 1X was. This is where the difference lies between W-CDMA and CDMA2000, the upgrade costs for W-CDMA are huge, and come to think of it, there's still not a working W-CDMA system in commercial use.
As for the Japan numbers, KDDI seperates the 1X users from "normal" users, and the number of minutes each uses, so no, these people aren't just people with 1X phones using voice.