Euro NCAP actually mandates that a following distance should be part of adaptive cruise control. A lot of manufacturers have turned this into a distance meter on the dash, in addition to the automatic braking. When I test-drove a Renault 5. I could see a little bar graph measuring how close I was to what the car thought was safe. Which turned out to be a lot closer than I would be comfortable driving! That is, the car would have allowed me to get much closer before it would have activated any automatic braking.
(the irony of looking at a meter on the dash to duplicate a piece of information I should be very clearly seeing out of the windscreen was not lost on me, though)
Automatic braking is a last resort to prevent serious injury to the occupants. That's not the same as safe following distance with adaptive cruise control. The closest my Tesla will go at 60 kph is about 15 m (three car lengths for my Model S) I think. I'm not sure because I normally keep it at maximum separation, about three seconds (50 m at 60 kph).
(the irony of looking at a meter on the dash to duplicate a piece of information I should be very clearly seeing out of the windscreen was not lost on me, though)