You want a planet that is geologically active enough to produce volcanos, plate tectonics, and Van Allen belts. But what if the line between "happily geologically active" and "prone to extinction events" is way too close together for comfort? See, for example, the Deccan Traps. How much bigger would that event have to have been to make the planet completely uninhabitable?
Mother Earth has occasionally been a very tough mother. Happily, not so tough as to have wiped out all life on the planet. Planets that are just tough enough may be more uncommon than we think.
(I continue to optimistically assume that we can avoid wiping ourselves out. Your mileage may vary.)
