I generally agree with you, but electric work is different. Except if you’ve wired your whole house by yourself, having someone qualified and legally responsible for rewiring is important. Even if their own work is minimal, they also take responsibility for not fixing the previous work if there was anything that should have been noticed, and it’s a role you can’t take.
On insurance, as you say their interests are opposite, and you need to be defensive about how to deal with them. Not having insurance on a house is not an option, so making sure you have a standing ground when shit hits the fan is pretty reasonable in my opinion.