As far as I can remember, this whole radial-on-drive-side thing was started by Mavic when the Ksyriums were introduced. Of course, according to Mavic's ad copy, this "Isopulse" thing was the cat's meow. But really, Mavic had to do that because their fat brick-in-the-wind aluminum spokes were too thick to be laced crossed on the drive side without running into cassette and/or derailleur clearance issues.
So essentially, radial lacing on the drive side is a
workaround prettied up and sold as a "feature". I mean, why would anyone want to add weight to hubs so that it is strong enough to transfer torque to the non-drive side, when the drive side flange is perfectly capable of doing that already without any reinforcements? It makes no sense at all in terms of design optimization.
Sheldon Brown discussed the merits of half-radial (that's with radial on the non-drive side)
here.