If someone gives me a take-home assignment that I spend 4 hours on, there is no commitment of time on their side. They may decide to not even look at the results. They may spend five minutes on it.
That's exactly my problem with take-home code challenges. If I go to an interview, and they waste my time, they have to waste their own. But with a take-home assignment, they can waste my time without wasting their own. That may lead them to be more wasteful of my time.
If that’s the case - sure. But that’s not inherent to code challenges. I evaluate results of challenges at work, they require 2-3 hours of candidate time and it rarely takes less than half of that time to fully evaluate and form a recommendation.