I'm not a fan of over-regulation, but there are definitely some public good issues with plumbing in particular which justify some scrutiny by the state.
For example, a bad/ignorant plumber could build a system where small quantities of used water can be reintroduced to the mains supply (the public health consequences of which could obviously be horrible).
We could help the poor more by providing free training/licensing, or just by having a more generous welfare system so that they could buy it themselves. Sacrificing useful regulations is actually a very costly way to help the poor.
For example, a bad/ignorant plumber could build a system where small quantities of used water can be reintroduced to the mains supply (the public health consequences of which could obviously be horrible).
We could help the poor more by providing free training/licensing, or just by having a more generous welfare system so that they could buy it themselves. Sacrificing useful regulations is actually a very costly way to help the poor.