I think the biggest difference isn't age, it's that childcare also happens during the summer, not just during the school year. (And of course the lack of any particular educational curriculum.)

Is that a meaningful difference, though? Schools were originally open all year round, but the hot summer classroom eventually was deemed an unsuitable place to occupy, thus schools decided to compromise by closing during the hottest months.

Since the advent of air-conditioning, there really isn't any good reason to close schools during the summer. But, like the internet bit before, we've just never bothered to stop and actually think about what we're doing. We carry on with the status quo simply because that's what we did in the past. Not because it makes sense, just because that's what we do.

But in establishing subsidized daycare now, we don't have to think about the time before air-conditioning was invented. We only have to worry about the constraints we have today. Hot summers are not a practical problem as of right now.