I don't disagree with anything you have said (I wouldn't dare...) However there is a purpose to this kind of suit. I use a BMW coverall every day to commute. I wear a uniform at work and have nowhere convenient to change in my current role. The coverall is perfect as I don my uniform (including PPE boots) and then step into the coverall, zip down the legs and I immediately am ready in a fully waterproof suit with full protection. When I arrive at work I step out of it (without having to go to the toilets to strip down to my pants) and I'm ready for work. Layer up accordingly for the time of year.
Granted I never use it for rides etc for most of the reasons you state but for commuting they are spot on. Good for journeys where you can step out of it, grab a jacket from the pannier and completely loose the appearance that you have just ridden a bike there. I appreciate you can do similar with basic waterproofs however they rarely come with all the body armour and abrasion resistance. Bloody pricey though!!
Neil