Looks like some safer adapters come with reinforced skewers too, which is interesting:

https://ebay.us/m/ERppMa

For steel, though, people just weld in an extra support:



I've heard 70's/80's CrMo frames aren't as tough as people expect because that more expensive grade of steel was used to allow thinner tubes and a lighter bike rather than to increase strength. Also mountain bikes back then didn't do all the ridiculous jumps and drops and obstacle courses and black diamond trails and whatnot modern full suspension mountain bikes get up to.