I'm reasonably proficient with a Colt 1911: either a Commander or full size in 45 acp.
I don't need more than the 8 rounds available with a 7 round magazine.
If I can't solve a problem with the number of rounds in the gun, I'm in a situation more ammo won't help.
I've never heard of a civilian situation in which more than a few shots were necessary, let alone a reload.
If anyone can point to such an event, I'll reconsider.
If I went to a crime scene or to participate in an arrest in an official LEO capacity, I'd carry an extra magazine : an additional 7 or 8 rounds.
Never in a civilian capacity.