They are (largely) regulated, most of them come under the insurance and auspices of British Cycling which has guidance/rules for organisers and they’re reasonably self-limiting in the fact that if you try and put three Sportives on in the same area on the same day, at least one will fail to get any entrants. Or the route clash will be picked up by local cycle clubs or bike shops or by regional British Cycling staff and passed on to HQ.
There are of course still the odd few cowboys who run an event without any notification, take the money and run but most organisers are reaosnably sensible and they obviously aim for the areas where they get the biggest take up – of course it’s Box Hill area this year but watch what happens in Yorkshire next year!
But yes, some riders behave like total **** – there seems to be a minority who don their lycra and immediately lose all common sense and manners; ride 3 abreast, swear at car drivers, drop gel/bar wrappers, speed through villages and whap their cock out in public to piss in a hedgerow.