Right, but what I wanted to highlight - a person might be able to code quick sort algorithm or breadth first search, but unable to get paid doing real world coding - when it is the client or employer who needs to be satisfied.

So basically when you have a choice of being unemployed vs doing PhD and getting some studentship, you obviously prefer the latter path.

And I believe there are quite many people who can "code" but unable to get paid.

It's hard for someone in anything remote to math/science without coding anything in their entire undergraduate life.

It's like you say no one can be admitted to a PhD program in US without first learning some English.