We do actually keep cars out of areas with lots of people here. And the media headlines always refer to a "car" driving into people without mentioning the person behind the steering wheel. Whether that's the better than addressing the root issue is another question though.

We also don't allow car use without a license.

In the end what matters if allowing something is a net positive or not. Of course you can have more precise rules than just a blanket ban but when deciding and enforcing those rules is not free that also needs to be considered in the cost benefit analysis. Unless you can propose how projects can allow "good" contributions without spending more time on weeding out bad ones, a blanket ban makes sense.