I'm not sure why you think this is something about tech specifically or even something recent. Most hiring has always been about knowing people and/or some other signal rather than walking off the street other than in a really would-be employee's hunting environment.
ADDED: To be fair, it's probably the fact that, in tech, junior people coming in without any real credentials or otherwise out of the blue at this point probably face a lot of headwinds--especially relative to the last decade or so.
I know a few mechanical engineers and they haven’t seemed to have the same hurdles. One works in the car industry, a few others in industrial areas, they all switch jobs by simply applying online to their desired companies.
I know some accountants and people who work in logistics who cleared lower bars to get interviews, though I suspect the accounting shortage had some to do with the former.
Finance is very networking heavy but clearing their interview process in some respects sounds easier than the leetcode engineering grind but that may not be representative of the situation as a whole.
Networking never hurts, no matter the industry but tech has a self inflicted wound around hiring practices few other industries seem to have
ADDED: To be fair, it's probably the fact that, in tech, junior people coming in without any real credentials or otherwise out of the blue at this point probably face a lot of headwinds--especially relative to the last decade or so.