I read an interview, probably from NPR, but I can't find it at the moment. The upshot was that caring for infants is insanely expensive, since they need one-on-one care pretty much continuously.

But parents can't afford that cost, so, essentially, the price they charge for infant care is a loss-leader, and parents of older children (who need less supervision and thus more favorable staffing ratios) subsidize the cost of caring for infants. Daycare operators are barely keeping afloat.

Edit: Ah, here it is: Baby's first market failure