There are several factors here,

1. A candidate with an advanced degree (theoretically) requires less training/can be trusted with more important work. Also training an employee is a large economic cost (ie loss of potential profit), companies want to minimize training

2. Most people who have degrees have loans, a debtor makes a reliable worker because they need your paycheck

3. HR famously never understands the actual job and they take the qualities a perfect candidate would have and posts those as required

it's just plain old supply and demand

from a marxist view, there is something to be said about how the boom/bust cycle of capitalism incentivized people to get college degrees (and in recent years, tech-oriented degrees in particular) during the boom phase, which created an oversupply that more than meets the demand now that we are in/approaching the bust phase

In addition to what others have said, liability is also a factor. If you don't work out, it's because you somehow lied about being able to do the job and not that their training was inadequate or that they failed to prepare/equip you. Additionally, less training is required theoretically, which means less cost on the investment of a new employee. Less risk overall for presumably better results.

Lack of experience also means they have deniability not to hire someone. I've had interviews go south immediately when the interviewer realized I was LGBTQ+ (stealth fail), but their stated reason was that I didn't have enough experience with MacOS. I've done volunteer work in my field for the UN using MacOS, but alas, I was "too inexperienced". The higher the requirements, the safer those sorts of dismissals are for them to make.