I'd argue that those higher standards/costs for raising children are the effect and not the cause.

We (need to) invest more into their education because uneducated children/adults have little or even negative value as workers (especially to their parents), this was not the case two centuries ago.

Children appear to be a "luxury" nowadays because there is no longer any expectation that they "net contribute" to their family economically (might be a positive change ethics-wise, but this is a huge shift in incentives for parents).