I think a lot of people choose to have kids too late. I know many people who had their first child in their early to mid 30s. That does not seem optimal to me, and not just because Uma was born 4 days before my 27th birthday. Consider how old I will be when Uma is at the normal college graduation age: 49. That's pretty young. Suppose Uma gets married at roughly the standard age. I'll be in my 50s. That's good, too. Think ahead to the far future where prospective grandchildren do the same things, assuming it's at roughly the same ages. I'll be 76 when my first grandchild graduates college, and about 80 at the wedding. If, instead of 27, the first child happened at 32, I'd be 86 and 90 respectively when those things happened, which calls into question whether I'd even be alive. And that's just the first child. Most people wait a couple of years at least between children. Then consider how it can take time to conceive as well as the scarily-high miscarriage rate. To the extent that one can even guess things like that, I have a pretty good chance of being around and being healthy until Uma is well-established on her own 1 .
The other major factor is the age of the mother. Pregnancy and health issues of various sorts are much more frequent once the mother is 35. If you want two kids, you have to have the first one in plenty of time for the second one to be born before Mom is 35. What if you decide you like having two kids so much that you want a third? If you started at 32, you have some tough choices to make. There's also the issue of women who stay home while their kids are young. You can certainly get further along in your career before having kids by delaying, but that means you'll be even older when it comes to returning to the work force, which can be rather intimidating.
I'm not saying that everyone should do this. I'm just suggesting that people who have a choice examine the consequences more closely. People who aren't financially stable ought to wait. So are people who aren't in a very stable relationship 2 . Ditto for people who haven't finished their education. There are any number of really good reasons for delaying, but you should make sure you've thought through the consequences, including the options it forecloses. Having a child is easier at a younger age, and when you have your children has ripple effects through all of your life and all of theirs. Delaying has clear advantages for financial stability and getting out your last ya-yas as a footloose and fancy-free youngster, but it comes at no small cost.