I'm 34, so not quite the defined age for this section of the forum, but I definitely relate to the whole "waiting" life choice, so thought I'd share my thoughts.
I chose to wait because I had places to go, things to do, a world to explore - and I wanted to do that for myself before I became a parent.
I also wanted to be very sure that I wanted to be a parent. That has always been a huge decision to me and one I take really really seriously. No having a family just because that's what you are supposed to do. I wanted to be really sure that I wanted to be a mum and that having my own biological kids (ie, experiencing pregnancy myself) was the way I wanted to experience being a mum.
I'm expecting #2 this year and my husband and I are pondering if we want to try for a #3 or not. We are also debating whether that hypothetical #3 would be adopted or biological.
A huge part of that decision is financial. We waited, both have great, fulfilling careers and are financially stable, but I am still gobsmacked by how much of a hit the household income takes through either childcare costs or having one parent stay home. I don't know if we can afford to have another if we want to do the same kind of savings for education, family trips and experiences, etc. - and this is from a couple who make over the median household income and live quite a frugal lifestyle. It's a lot better once kids are in school, but the childcare costs for those early years are staggering (at least where I live they are). Money isn't everything, but I don't want to be stressed out and broke while I try to raise my children. I want to be frugal, but able to offer my kids extras like music lessons and sports and all those sorts of things.
It's not an easy balance.
And the whole other can of worms for me?
While we have made huge strides in a woman's rights in the workplace with maternal/parental leave, it still hits a woman way harder in terms of income and career when a baby arrives. I think that is slowly changing, but right now I think a lot of us still see maternity leave as a scary kind of gap in our work lives.