So, it's apparently to protect the hospitals. While I've no idea of the situation in Austria, in most Western European countries ICU occupancy is largely unvaccinated people and severely immunosuppressed people.

So once you're close to ICU capacity you have three options: - Ignore it, likely leading to a lot of deaths. - Full lockdown - Targeted lockdown of the most vulnerable population (similar to 'cocooning' of elderly in the early stages)

Obviously, none of these are great options, but they're the choices a number of places are now facing.