For one, the industry never did professionalize to begin with, certainly not in the way accountants, lawyers etc did. We never had any real body that could certify proficiency, which is what contributed to companies having to resort to leetcode and other such styles of interviewing.
Additionally, it wasn't software engineers doing this, but people looking to cash in on students looking to get a 6-figure job. They were business people, not software engineers.
Management types really really really loathe software developers for making good money, and have spent decades now jumping at any advertisement that suggests it can undercut the salary of your current crop of engineers.
Devaluing software developers has always been the point. Whether you take the cynical view of "They resent us for being expensive" or the apathetic view of "Capitalism simply wants to eliminate any and every cost by definition"