“Travel with two year old”

I live in Japan, and I sometimes read the subreddits related to travel to Japan.

There are many posts to the effect of “Where should I stay/what should I do in Japan with a two year old/11 month old, etc.”

And the answers (from people who did it) are to visit parks, and to not plan to see or do too much because it’s hard/tiring to drag the child around in a country where people (in cities at least) use trains or walk a lot to get around.

I just wonder WHY? Why are they traveling internationally with a small child who won’t even remember any of the experience? It makes no sense to me.