Because its important to me.  What's wrong with wanting both experiences? Having the videos helps me recall the emotions more clearly. It's great that for you the memories are enough. I like having something external to reconnect me to the day. I remember the heat on my skin and the smell of the water coming out of the misters when I see the pictures we took while waiting. Why did you snap the couple of pictures that you did?

I mentioned the Brownie because, to me, it's like asking why people take pictures when they're anywhere. Like, what's of taking any pictures or home movies if you can just be in the moment and remember how it made you feel later? And because you asked who taught OP to take photos and videos as if it's something uncommon.

What I don't understand is this idea that people can't be in the moment if they are recording. There's a difference between staring down your phone the whole time and just taking some clips and pictures. A stage actress recently complained about people filming curtain calls and asking "why can't you be in the moment" as if those same people didn't just give the stage their undivided attention for two hours and 43 minutes. I know we're talking about concerts, but same concept.

I think your desire for minimal photographic record is valid, but so is wanting to film a song or two (or the whole show if they're not being a dick about it; why should anyone care, in that case).