Earlier quoted context omitted.
A PhD is the most common way to gain the experience and context needed to work professionally on compilers. If there aren't many PhDs, then the supply of people with the experience needed in practice is going to be low, even if there are also people without PhDs who can do it.
No university class teaches modern compilers and the state of the art is in open source projects. If someone is interested in compilers, they don’t need to get a PhD in order to learn. Many major companies that maintain programming languages do not require PhDs in order to work on their compiler teams; they are willing to train you on the job. The supply of people interested is just low in general, and if you are bia…
Yeah... hence why you need a PhD. 90% of domain knowledge in this field isn't even written down - you have to sit down with a wide range of people to learn from them - which you get to do on a PhD.
> Many major companies that maintain programming languages do not require PhDs in order to work on their compiler teams
They don't require it... but look at who's actually there and how many of them in practice have a PhD.
> if you are biased towards people with PhDs and preexisting experience for junior hires
As I've said elsewhere I've taken on people with no high-school diploma and zero experience in the past - I'm not personally gatekeeping.