Like you longfemur I grew up with lugs, and welding didn't really show up until later, though bikes have been welded for possibly 100 years, the TIG revolution brought it to modern quality only in the last 20 years or so. I guess the fact crap and art was lugged when I was a kid has meant it isn't a high end only thing to me.

I think it is harder to weld than to braze. TIG is not easy to pick up, though to any profesional it's kinda irrelevant since one puts in the time and turns out the product. Skill beguiles amateurs, but pros don't think about it. We all learn to write at some functional level and we never obssess about the skill involved once it's there.

Metal is very easy to repair since strong butts can be made. Repairing a frame is probably pretty rare these days, if it comes up though, I don't see any advantage to repairing lugs. One can pull drops and such when making adjustments, but to actually do a major repair on the frame of another builder is going to make a mess once the paint is on.