Averages don't count when a single impact can cause extinction of Humanity.
150 per year is meaningless. The point is that a major impact can do to us what one did to the dinosaurs: exterminate us completely. Consider two scenarios.
Earth population constant at 6 billion.
(A) 6,000 deaths per year for a million years: total 6 billion; results on humanity: nil
(B) 6,000,000,000 deaths in the same year: total 6 billion; results on humanity: extinction
Which is the worse of the two? The second could happen at ANY TIME. Without warning. Surely it is something to consider.