Immediate feedback from a good autograder provides a much more interactive learning experience for students. They are able to face and correct their mistakes in real time until they arrive at a correct solution. That's a real learning opportunity.
The value of educational feedback drops rapidly as time passes. If a student receives immediate feedback and the opportunity to try again, they are much more likely to continue attempting to solve the problem. Autograders can support both; humans, neither. It typically takes hours or days to manually grade code just once. By that point students are unlikely to pay much attention to the feedback, and the considerable expense of human grading makes it unlikely that they are able to try again. That's just evaluation.
And the idea that instructors of computer science courses are in a position to provide "expert feedback" is very questionable. Most CS faculty don't create or maintain software. Grading is usually done by either research-focused Ph.D. students or undergraduates with barely more experience than the students they are evaluating.
The value of educational feedback drops rapidly as time passes. If a student receives immediate feedback and the opportunity to try again, they are much more likely to continue attempting to solve the problem. Autograders can support both; humans, neither. It typically takes hours or days to manually grade code just once. By that point students are unlikely to pay much attention to the feedback, and the considerable expense of human grading makes it unlikely that they are able to try again. That's just evaluation.
And the idea that instructors of computer science courses are in a position to provide "expert feedback" is very questionable. Most CS faculty don't create or maintain software. Grading is usually done by either research-focused Ph.D. students or undergraduates with barely more experience than the students they are evaluating.