Thank you for raising the point about SN, LRD. I'd missed that in the OP.
Tehtersend - I often think forlornly of Iceland (as was) and Bjork.
Personally, I think that behind the move to older mothers is a shift in economic structure. Women have started working in large numbers and we haven't noticed how hard we are all working, to achieve what is perhaps a lower standard of living than that of our parents's generation. It doesn't yet feel as though it's lower, because it's masked by the fact that in many households, there are now two adult incomes where before there would have been one.
Yes, women working has brought greater autonomy. I do think that. But we haven't noticed that things are also a lot tougher economically. The economic uncertainty, and fear that drives the delay of that first child is massive.
The saving for a mortgage before having a first child is particularly ironic, given that I think it's unlikely many of us will get through old age with anything substantial to "pass on".
I think there's also a touch of fear-of-economic-uncertainty (and basically a mistrust that there will be a welfare state in years to come) that drives the push to find the Right Partner ... though I will concede that there is also a fair bit of emotional and romantic stuff in there too. 
Basically, I think if we felt we were living in times of plenty, with lots of fulfilling work opportunities, low work hours, wages that could purchase desirable leisure activities quite esasily, we'd be a lot happier about taking the "risk" of having children, and do it without the economic steel-girding we try and put in place, because having a child/ren would be less of an economic risk.