You are right, I'm always against this.
Hard to keep that separated when both of those things run the majority of your life. I am 36 and not married, still single and no kids. So I am fastly approaching 40 myself. Its as much as a choice, as well as family trauma/PTSD unrelated to having a gf or being married, which has put me off from ever doing so. It is not from the lack of trying though, things ended between me and my ex-gf back in october. Who knows the real cause, probably both of our faults. a mix of her insecurity and my PTSD/trauma resulting into communication breakdown. I also have Aspergers which complicates things as well.
Biologically? the older I get, there is something inside me that keeps pushing being more and more driven into finding someone and starting a family. But at the same time, I have a lot of past trauma from my previous family life before moving out and being on my own that I am still healing over. Honestly, I dont think itll ever heal and its just scars I will deal with for the rest of my life most likely. I always told myself that "Oh, ill have time someday to start a family" but that time is rapidly running out, unless I want a gross age-gap then id be looking at adoption. I am the end of my immediate families blood-line too. Without me having kids, the family doesn't continue on. I have a brother but hes fully autistic non verbal.
But, I also know getting married/starting a family comes with its own set of drama, insanity and complications... And in the end, you still may end up dying alone! Double-edged sword.
Anyways... I have only been on my own for almost 8 years so I am just now getting to the point where I can finally decompress through all that insanity.