Why do you think memories are kept?
It’s undoubtedly true that memories are Golden. Memories are times that happened and are captured (not necessarily with a camera) that resonate with triggered actions (or just because you feel like it).

Why memories?

Reminisces. You can always look back at when you’re smaller or much more stupid and just smile to yourself.

Lessons. If you keep track of yourself (using a journal) and you look back to it and study it well, you’ll be able to figure some things you did right and other things you did wrong.

Laughter with friends. Especially when there’s a reunion. It’s one of the best feelings when you with your friends and family and someone brings up something funny from years ago (except that time you were very stupid, then you might not laugh or probably laugh too hard)

Throwbacks. Our generation has dedicated Thursdays to that purpose (though it can be on any other day). Just go check Facebook and scroll to the top and you’ll get the throwback picture of almost anyone. Thank me later.

I mean, did you see the #10yearchallenge pictures, oh lord😂😂😂

So why keep memories? Question is, why not keep memories.

How?

Journals. Should be the oldest form of keeping memories and still one of the best ways to do so till date. Could be daily or weekly or just occasionally.

Brain. These are the memories we only remember and talk about with people that were also there when it all happened, no single picture but the memories are clear and concise.

Pictures. Most common ones for memories today. Smartphones made it easier, taking pictures back in the day was a really stressful process relative to the way it is today. And images can be stored in cloud storages to preserve till the right moment.
And life got easier when the word selfie was added to the dictionary.