You don't always immediately know which ones will be important.
Today you might take 10 photos of your family and keep the best one where everyone is smiling.
But 10-20 years from now you will probably appreciate having kept the other 9 where the baby is crying, the kid is making a face, and grandma has started to wander off.
I've passed through the other end of this. I spent a few hundred hours scanning my father's and grandfather's slides, negatives, and prints on high-end scanners in 2010. There were thousands of images, and since then that number has probably increased several orders of magnitude with digital cameras and then phones. The sheer number is beyond human comprehension. Now that images are so trivial to make, I value curation much more than shear number. I suppose it's always a quantity vs quality thing.
Today you might take 10 photos of your family and keep the best one where everyone is smiling.
But 10-20 years from now you will probably appreciate having kept the other 9 where the baby is crying, the kid is making a face, and grandma has started to wander off.