No, Not traveling with a child. I'm sure this is just a $ thing. The seats are obviously held for people who are willing to pay a full fare class or have a "Gold" status. They appear to block the bulkhead seats downstairs for the same reason.
As to Aussie_flyer's comment: I've never experienced any airline that charges for advanced seat selection . At least not on any of the airlines I've traveled on (Thai, EVA, Cathay, United, Delta, JetBlue, Alaska, Singapore, Swiss)