Today's opulence outrage from the high-tech sector is that Facebook is planning a massive apartment complex that will feature doggy daycare but no child care center for actual human children. That's a great jumping off point for discussing the genuinely pressing issue of exorbitant child care costs in the United States and the critical strain they place on middle class incomes, social mobility for the poor, and ultimately the continued existence of the country.
But if you want to know specifically why something like this might happen, I would suggest a stroll through the California Department of Human Services helpful "regulatory highlights" document offering you a glimpse of what it takes to legally operate a child care facility in the Golden State. It's not that these rules are necessarily unreasonable. You can see why this would be a regulated industry. I'm not entirely sure that "between meals, snacks must be available for all children" and the snacks must "include servings from two or more of the four major food groups" is necessarily something that needs to be legislated, but I dunno maybe it is. The point is that these rules are pretty tough. Complying with them would be a big pain in the butt. So throwing this in as a perk would be a much heavier lift than setting up a facility where someone can take care of your dog.
The flipside of regulatory compliance is that you end up with a lot of potential liability in lawsuits. There's a whole specialty industry of providing insurance to child care centers.
The upshot is that this is a pretty daunting proposition. If you try to give your employees some free ice cream as a perk and it turns out that the ice cream offering ends up being kind of below average and people don't really like it, at worst you've wasted some money. But if something goes wrong with your child care operation, you're exposed to a lot of front-end compliance issues and back-end legal risks. If you are specifically in the business of running child care centers, that's just life. But if you're trying to keep people focused on running a software and social networking company, you might decide this sounded like a good idea when you first heard about it but now that the lawyers have looked into it it's not such a great idea. How about pet care instead?