I carry a spare mag at all times because the malfunction drills I do assume having one handy. If tap-rack-bang doesn't clear it, I still have the rip out mag-rackrack-insert new mag-rack-bang available and well drilled in.
The combined capacity of 14+14 is not entirely optimized but I don't mind the extra weight. Oftentimes I download to 13+13 just to save the mag springs a bit. I would be entirely happy to have some 1911 variant with a 7-shot mag and another to spare, but that's not what I spend my training time with.
I'm an A class IPSC shooter and I regularly spend considerable range time with a CZ SP-01. So my carry gun is a CZ D Compact with the same trigger pull and grip angle, and equipped with the same sights as the competition gun. And it just happens to come with that 14-shot mag.
Now, inanimate objects do not make me do things I don't consciously decide to do. I don't feel a burning need to spray everything moving with bullets just because I have several available.
I've read this thread with great interest and respect to the experiences and knowledge shared, but there seem to be some quite baffling straw arguments, exaggerations, projections or sweeping generalizations on top of the very sensible undertone here.
1946, could you sum up in a two-sentence argument your exact point against carrying a spare magazine? I'm at a loss with your reasoning so far.