Why abuse? Well, let's say they have three solid candidates. They ask each to do an assignment. Would I do a 6-hour project for a 33% chance at a job? Maybe, especially if I really wanted that particular job.

Now let's say they have 30 candidates that they ask. Would I do 6 hours of throwaway work for a 3% chance at a job? No - not knowingly. If I'm an average candidate, I'm going to have to do that 30 times to land a job. That's 180 hours, or more than four full-time weeks of throwaway work. That's an abusive process.

Could I spend just as much time interviewing? I could, but there's a difference. If I'm interviewing with you, you're there talking to me. You can't waste my time without wasting your own. Whereas with a take-home assignment, you can waste my time but waste little or no of your own. As a result, interviewers (usually) pay some attention to not doing needless interviews, but pay less attention to not asking for needless take-home assignments.

Not just that: At every job where I interviewed candidates, HR expects some kind of feedback beyond just "hire"/"no hire". At least some bullet points of highs and lows, red flags, etc.

If nothing else, this helps protect the company from false allegations of illegal discrimination by having documentation for why a particular candidate was rejected. It also helps recruiters to know if they're finding candidates who are "close to what we want" or "not even in the ballpark".

Now, I know that some interviewers can be fairly blunt in their feedback, so you'd not necessarily want to just copy-paste it to the candidate, but the point is: that feedback already exists. The recruiter/HR just needs to (maybe) sand off some of the rough edges.

Well, it's a good lesson to have gone through though. If I'm ever in a situation where I am asked to evaluate others in a similar fashion, I'll be sure to leave detailed feedback (if they want it), now that I know what it feels like.