If you'd like the answer, the belief originally stems from watching hundreds of millions of people die of smallpox
https://historyofvaccines.org/blog/timeline-of-vaccination-m...
Statistics agencies have to massage the raw data very significantly in their models to make it look like vaccinated individuals catch covid less often than unvaccinated people.
When one drives recklessly, we know the result, bodily harm to themselves and or others. When one takes a new vaccine with limited testing and emergency approval, we don't know the result(s), yet.
By that logic, every set of choices one could have that affects others should be regulated or overseen?
Moreover, that comparison is predicated on the belief that vaccines prevent transmission. There has been no sufficient data (to my knowledge) that backs up the claim of them doing so.