That's a silly argument. You could just as well say that the more things you launch that aren't a passenger-loaded vehicle, the more likely you'll have worked out the glitches by the time large numbers of lives depend on it.
A mission to Mars is guaranteed to be the most complex space mission ever attempted. Every additional rocket you need for the mission adds complexity. Complexity is the enemy of reliability.
What happens to your Mars departure window when the rocket carrying your life support system goes off course and is destroyed by the range safety officer?
