This is a legit concern. But I think it's rooted in processes that don't make work-sample challenges determinative, and for which candidates can only lose and never win from taking them. A firm that standardizes its whole process on work-sample challenges can't deploy them abusively and still recruit successfully.
Meanwhile, if you commit to relying on challenges, you have a pretty major incentive to put time in to help candidates through them (if everyone bombs out of them, you don't hire anyone; if you're not rigorous, you're hiring randomly and you know it). We'll spend $100 and several hours for blind candidates (or at least: for every candidate we'll actually let into our hiring process) because we need the process to work, and to actually highlight good fits, in order to staff the company.
As always, a qualification process run haphazardly won't work and will alienate people.
Again, my suspicion is that most companies that do take-home problems are cargo-culting them, and not actually hiring based on their results. Rather, they're relying on the same interviews everyone else does, and using the challenge as a very elaborate form of FizzBuzz.
Meanwhile, if you commit to relying on challenges, you have a pretty major incentive to put time in to help candidates through them (if everyone bombs out of them, you don't hire anyone; if you're not rigorous, you're hiring randomly and you know it). We'll spend $100 and several hours for blind candidates (or at least: for every candidate we'll actually let into our hiring process) because we need the process to work, and to actually highlight good fits, in order to staff the company.
As always, a qualification process run haphazardly won't work and will alienate people.
Again, my suspicion is that most companies that do take-home problems are cargo-culting them, and not actually hiring based on their results. Rather, they're relying on the same interviews everyone else does, and using the challenge as a very elaborate form of FizzBuzz.