Assuming someone’s informed, I think it’s a combination of strong desire for a child, plus greater hope for the future than I have. I don’t think I’d go so far as to say that they “care nothing”. I know people with young children, and they’re certainly very loving parents.
As you know, kids are smart - but they’re not mind readers. They might pick up on that regret and interpret it as resentment. That would be bad. Just make sure they know you love them, and be the best parent you can. Maybe things will work out somehow.
Does that 53% include adults that decided to have zero children? The title implies not so I wonder how many adults in total are deciding to not have kids/more kids.