Would we want them returned to the shelves though? Both sodium chlorate and copper solutions are harmful to people as well to the environment
Agreed, Sodium Chlorate is toxic if ingested but no more so than many other products that are still licenced for sale, let's face it bleach is pretty harmful if ingested. There are still copper based products available for sale so it is not necessarily correct that Bordeaux Mixture and some copper sprays were banned for environmental or health reasons.
More likely is that the profit to be made from selling these products (some of which are now in the public domain) will not satisfy the manufacturers' greed in light of the cost of licencing them. It is easier and more profitable to release new products into a now 'closed' market and reap a higher profit margin.
Any chemical can be dangerous if used incorrectly, but you can't dismiss the environmental impact of some of them. The build up of copper over time, in soils that have been treated with sprays like bordeaux mixture, is pretty well documented. Home growers may use may a lot less product than your average vineyard owner, but there a lot more of us dotted across the land.
Manufacturers are in it to make money. Why exist otherwise, but unless they can corner the market on some new wonder replacement, it is not in their interest to see stuff banned. Some slow selling lines have gone because the economics just didn't add up against licensing fees. Most of stuff now off the market has been because of pollution of soils, watercourses, problems with run-off or potential health threats.