Like with roads and cars, radio spectrum is a very limited and very shared resource, and there has to be some regulation, or else some Elon Musk-type person would already take it for themselves for a commercial reason.
It's also self-policed, so that means that hams have to find the problematic entities and hope that authorities with legal power act on those reports.
The devices can also be uncertified (self-certified by a ham technically), so you can cause all sorts of havoc for many other entities, like actual emergency services (a case not long ago in US) or worse.
If you are not able, or for some reason or another don't want to get licenced, there are other ways to communicate, like mentioned meshtastic, which doesn't require a licence on ISM bands, or PMR/FRS radios (or gmrs in us, which does require a licence but you don't have to learn the radio basics for the exam).
Again, like with roads and cars, you expect others there to be mentally capable enough to pass that simple exam and follow the basic rules on the air. If not, they can get a bicycle and argue on the bicycle lane with other cyclists. And the ham exam is much cheaper and easier than a driving exam (in most developed countries at least, the driving one costs 1keur++ if you finish optimally, whereas over here, a full intro to ham course (a few weeks, usually on zoom) with a printed book and the actual exam costs <100eur, even less with a pdf instead of a book)
