I have kids; neither me nor the other parents I know show off our pictures of them. If we do, it's usually because we've been asked, or it's people posting stuff to social, which I don't think is quite the same. If I had to guess, it's an older generation thing. That said, I DO take pictures of my kids, but that's almost always exclusively for sharing within the family.
Apparently the average cost is $233,610. If you save all of that and assume that the child is 18 when the parent is 45, then there's another 20 years til 65, which is enough to more than double. So $500,000+ extra at retirement per child, or about $20k spending per year (if you can delay in-home care for 10 years and use higher estimates, its as much as 45K/year extra). Apparently average cost of in-home care is ~$60k/year. So not having 2 children and saving all of the difference could make-up for that.
At least in western countries it is pretty likely your children will move far away from you anyways. Sure, it's still nice to have someone, but it was far more valuable when you usually died in same town you were born in.