1: Kids. My wife and I waited to get married, and then were part scared after we got married, and part selfish and wanted freedom to play and travel, so we waited more. I don't regret our adventures at all, but after we had kids, I realized my fear was unfounded and we still had a lot of freedom to play and travel. 2: Startup. I wanted to start my own business my whole life, and I waited to try until I had enough of…
Be careful generalizing - this really depends on your life situations (including income/savings) and preferences.
For example, out of both our sets of parents there is only one (my MIL) that I'd ever want my hypothetical children to be around for any more than maybe an hour visit once a year, and she lives a 4 hour drive away. So there is pretty much zero family support for childrearing for us, which is a big factor in our choice to avoid childbearing.
I feel I have to preemptively defend my choice to keep my hypothetical children from their hypothetical grandparents - they are domestic emotional and physical abusers, substance abusers, mentally ill, reckless and drunk drivers, conflict seekers, emotionally unstable, behave socially inappropriately, don't respect boundaries, and create a toxic environment to be in. I grew up with that shit - I would only subject my worst enemy to it.