I won't share the name because I'm stating an opinion he might not want shared but a rather famous old time rocker hangs out here in PEI for most of the year (escapes the winter) and I asked him his opinion on the whole Metallica sound issue. While he is very disappointed in the mixing trends that he saw developing over the lifetime of his career, what I found more interesting was largely to your point.
To quote him roughly...
"First I stayed out of the mixing booth because I didn't know anything about it. I just wanted to sing on records. Then I got heavily involved because I felt it was part of my artistic development. Then I realized I couldn't hear anything worth sh__ anymore so I stopped getting involved except to try and explain the sound we were looking for."
I suspect Lars is in the same boat. Timing is similar so neither would have worried about or been 'uncool' enough to protect their ears in the early parts of their career.
