One of the costs, if you are childfree, is that you now go from zero dependents to non-zero dependents. This cuts off a lot of options in life: your remote job can no longer be done from Japan for two months in the summer or an island in Thailand for a quarter in the winter.

There is a huge value to being able to travel for long periods on short notice in the first half of one’s life. A pet mostly/usually prevents that.