I think one primary reason so many people are setting up home and having kids without marriage is the shift in social norms re when to settle down. In days gone by it was seen as desirable to get married rather than cohabit, to marry in you early twenties, to have kids soon after marriage. Homes were a bit more affordable.
These days it’s very difficult to get on the property ladder single, even as a couple. I’ve found it incredibly rare in my social group to find any woman who wants to have a family in her twenties, and most men I meet aren’t remotely interested in kids until their thirties, the ones I know who had them in their twenties had ‘accidents’. Marriage is seen as something you do in your thirties if at all. I know if I’d even considered marriage in my twenties people would have said surely you’re too young, don’t rush.
The upshot is, by the time you’re in an okay position for a child you’ve spent your twenties working on your career and trying to save for a house, therefore you’re in your thirties and well aware time isn’t on your side regarding fertility. After a few 2-3 year long relationships in my twenties with men who said they wanted kids but ultimately decided they wanted to wait until their mid to late thirties, I met my OH at 28. Then it’s a couple of years together to make sure you’re built to last, saving hard for a house, and boom you’re in your thirties, can’t justify spending money on a wedding cos you need it for a house deposit and won’t have enough left after for kids, unwilling to risk not having kids at all by waiting to get married.
In an ideal world I’d like to have been married or civil partnered before kids, though I’m not that fussed and didn’t ever really have a craving to marry. But at 31 having had so many relationships with guys who ran screaming from commitment I’m choosing to crack on and TTC while I still have a reasonable chance (I have fertility issues). Thankfully in a stable wonderful relationship and almost on the housing ladder, so could be worse. But I wouldn’t hang around planning a wedding (yeah I know the whole do it for a hundred quid thing but I feel if I’m gonna do it at all I’d like it to be at least a bit nice!) while my fertility crashes when I’d rather have a family than be married.
Planning to marry either during pregnancy or within the first year of a possible child’s life I think. But I can totally see how so many people have ended up cohabiting with kids not married. I don’t have a single friend my age, 31, who married before children.