Besides, speed cameras, especially in NA, enforce by punishment. Punishment that some people are unable to afford, because for some reason they coddle billionaires while letting a fifth of their citizens rot in the gutter.
Meanwhile, a traffic calmed school zone enforces proactively. Are you sure you’d like to risk scratching your brand new $50k truck’s pristine paintjob? A properly traffic calmed street will force drivers to face that question, and in many cases, they’ll answer the question with “no”, and slow down. Mission accomplished.