I don't know about the 80% but some of DIY guys like me have proper judgment in what is safe to do yourself and what is not...

If your weld is not in a high stress area and if a failure of your weld would not compromise the structural integrity of your car then I don't see why I would not do it myself.

For example I have welded the gussets on my LCA myself but I would never have welded my steering adapter for my Borgeson Box myself, I am not stupid!