The industry has been very biased; from 1940 there weren't many programmers, very quickly the number of programmers doubled, most had little experience. Through the 1970s there weren't many programmers with more than 5 years experience. As the number grew so fast, through the 1980s most programmers still had less than 5 years experience. Same through the 1990s. Probably still the same through the 2000s and 2010s and with how many people are learning to code, probably still the same now, most programmers have <5 years experience.

That means most employers have only ever seen developers with <5 years experience, working in teams of same, using languages and tools designed by and for same. How could such employers properly value 30 or 50 years of experience?