Taking photos is a nice way of keeping memories to look back on later. You can hang your favourite ones on the wall to look at now and then. However, we can’t take a picture (or video) of everything. For example, although your children are still little, they already have their own personality and their own interests. How would a photo or video capture those?
Time goes on like entropy keeps increasing.
Moreover, remembering things like these can be at least as worthwhile as keeping photos and videos. Over the years, they will grow up to be an adult who may want to leave the house and support themselves. This prospect may prompt the question as to what they want to be when they grow up. I personally didn’t like this question when I was little because I had no idea. However, adults may be curious anyway and while we may not know what career they’ll want to pursue at least we know what interests they have right now.
I will argue here that, just as we take pictures and videos to look back on later, it can be an equally nice idea to have a dedicated book in which to write down the things your children do, say or show an interest in over time. If you provide a date for each entry in the book then you can even figure out how old they were when they did that or when they had that interest.