At the earlier ages stuff doesn't even come close to being useful for a year. I remember going to a local charity shop and buying a sackful of baby-clothes. I paid €10 for a huge bag and I remember that some of the same stuff got donated back a few months later - having never been worn.
Babies can grow so quickly that buying clothes used and sharing stuff amongst other local parents is the only sensible thing to do.
As with most gifts, the giving of presents is often more meaningful for the person giving.
The save with kids toys. The parents are really buying it for themselves, perhaps to express their feelings.
As an aside, the parents are also learning. No one is born with experience, so experimenting witj things until you get it right, happens with kids stuff too.
A side effect of birth rates and other demographic trends, people no longer have a huge network of friends and relatives with kids, to talk sense into us, and to share outgrown stuff. When I was an infant, my parents probably had a dozen other families with young kids all living on the same block. You also experienced the baby-hood of siblings and neighbors while you were still a kid yourself.
As a parent, I look back and think how much time and money I've wasted on things and actions my kids neither wanted nor remember. I look at my current life and wonder what I'll feel that way about in the future. Unfortunately, it's hard to tell what is worthwhile and what is not at the time.
As another parent, I completely agree. Of course, I also look back at all the time and money I wasted in my early thirties before I had kids, and also in my twenties, and also in college...
My wife and I joined a "free baby stuff" facebook group and got almost everything we needed for free.