I certainly couldn't answer why, but I wouldn't exactly be surprised if they added it to their lineup. $12 isn't that great by the way -- depending on your needs, have you looked at NameCheap.com? I used them for a bunch of my own domains, including their DNS service -- my needs are modest and the traffic hitting my sites is beyond low, but at less than $9 to register a .COM and free DNS it's really hard to argue with.

I used to use DynDNS (of course I've been using them since way-back-when in the modem days for dynamically updated sub-domain services), I got away from them just recently.. way too pricey for my needs, especially considering I needed to do multiple domains.

Google Apps for Work/GMail are both easy to integrate regardless of whos holding on to your records or hosting your name server, I don't think that should ever be an issue.

How's the "Google App engine"? I use Cloud9, and its unbearably slow -- but who knows what they pay for and how much they overload their machines with containers.