Are there any particularly logical reasons this setting is included with Pipe Networks, but not Pressure Pipe Networks?
A possible answer:Because that feature had not been added by the cutoff date for the Civil 3D development team to have their 2013 version ready for customer shipment. Autodesk works on deadlines, so sometimes new features, like Pressure Pipes, are released in stages. I expect to see new functionality included with Civil 3D 2014. Whether this specific issue is answered, who knows...
Delta Engineering Systems
Autodesk Authorized Value-Added Reseller
As with most here, I can certainly relate to the subject of deadlines and not quite being there. But, you read other related posts (i.e. No Swap Parts command, Missing Pipe Materials, extremely limited appurtenance catalogue, etc...) and it seems use of this feature isn't even remotely close to practical at this point in time.
It appears there's even a workaround just to get C3D to recognize and correctly assign the nominal diameter of the pipe to a notation. The default "Nominal Diameter Description" for a 10" diameter round DIP pipe is "10 in x 10 in" (What does that mean?), and as far as I can tell, it doesn't assign a "Diameter Inside" to use in a label style, either.
I know this sounds like sour grapes, but honestly I am as solid a proponent of Civil3D as anyone. With that said, this is the epitome of bad that comes with the good when it comes to Autodesk and Civil 3D. As much as I want to use this tool, the time spent setting up styles that'll become obsolete when content is added, and working around the clumsiness of the current release doesn't seem justified.
My biggest issue isn't that it won't be a useful tool, it's why it was released when it's obviously so far away from completion. I probably wouldn't have wasted the effort of this rant, if this felt like an isolated incident, but stuff like this has been an ongoing frustration.
Well, I feel a little better not that I've gotten that out of my system. Hopefully, it's not a completely meaningless 2 cents rant.
I can understand your frustration, and as Tim said above, there are features not found with pressure pipes that are found in other Civil Objects such as data shortcuts, swap parts, etc. I would highly suggest you make your thoughts known by following this link: http://usa.autodesk.com/adsk/servlet/index?siteID=
As for a limited stock catalog, please see this thread for more information: http://forums.autodesk.com/t5/AutoCAD-Civil-3D/Pre
Hope this helps!