Statistically, around 0.005 per year (note that there's a HUGE range of estimates for how common defensive gun use is, so there's definitely some error bars there). However that's still many orders of magnitude more than the average number of mass shootings that the average civilian gun owner is involved with.
So realistically the actual need for a large capacity magazine is zero?
The number of people who have used 10+ round magazines for self defense is greater than zero.
Used, or needed?
Who cares? It is a foundational human right. I don't have to prove my "need" for freedom of religion or speech, or right to bear arms.
Why is it a foundational human right? Who decides that? It seems to me that a lot of people disagree.
Human rights only exist because enough people believe in them. All of them, including free speech are up for debate and constantly need to be defended.
Both
I think part of the intention of the Second Amendment is to have a well-armed population that has the capability to push back against a government that has overstepped. Five or ten rounds isn’t going to help much there.
The need for a magazine is close to zero, but if you need one, you probably need, or would have a significantly improved outcome with, a 10+ magazine.
I don't know anyone whose house has burned down. Should I cancel my home insurance?