It isn't odd, at all.
It's great to see someone treat their child's privacy with some value, instead of using them as a way to endear themselves to virtual friends or get laughs and votes on reddit, while putting photos and information out there about their kid, without the kid's permission, that will be there forever. The rest of us had the opportunity to come to the internet in a time when someone wasn't putting our information out there.
Reserving accounts at places on their behalf, as well as domains, is also a smart choice. It isn't placing importance on anything. It is simply giving their child the option to have these things in the future. Hopefully, facebook won't exist when this kid grows up. But there's a chance it might. And if it does, then this kid doesn't have to compete with someone else taking the name. More importantly, it prevents someone else from pretending to be you.
I have to do this with my name, too. I have an account on Facebook, though I despise it. Same with the other big social networks and other things I don't use. I have been on the receiving end of someone who was upset with me (one a user I banned from my site after defrauding other users) and did things like make an account under my name and put awful stuff out there as "me". That would be more difficult to do if I'd already staked my claim to that identity (even if I didn't use it).
What these parents are doing is simply investing in retaining the tools with which their child will someday be able to safeguard their privacy and - if necessary - build their professional or other identity. It's worthwhile, today. It'll be even more worthwhile in the future.
Really, I fail to see how anyone can have any problem with this.