There's always trade-offs, concealing weapons and ammo is no exception. We give up freedom to enter certiain place, time, money, comfort, etc... We each have our own level of 'sacrifice' that we accept in exchange for the peace of mind that IF we need it, we would have it.
There are scenarios, real and imagined, that would require more ammunition than any of us could carry during our daily activities. I sometimes carry 50+ rounds of 9mm. Other times I carry 7 rounds of .25 auto. It just depends!
If I can I do carry one extra mag, sometimes two. It is always concealed.