I had my first kid with 38 and I wish it would have been sooner. I love having a kid now. But I worry about staying healthy enough to do the fun things I want to do with them.
And grandparents are a major factor, too. They are a great help, and also they really enjoy being with their children. Supposing my kids also wait until they are 38 to have kids, my odds at enjoying quality time with grandchildren are greatly reduced.
I'll probably be almost of pension age when my kids finish their education. That's another thing where I worry I might not be able to help them out as much as I could if I would still be earning money and connected in the business world.
It would perhaps be different if I had toiled and saved money all the time up to age 38, but I didn't. If you have kids, odds are you get more serious about those things.
Why do you feel that way? Biologically that's not really the way humans were designed. It's unfortunate that the modern first world economy and society is so incompatible with biology.
My mother waited until she was nearly 40 to have me, and as a result I was born with birth defects (I'm deaf). There is no way to deal with all of the risks.
There's advantages and disadvantages of both early and late childbearing. I don't believe there is an "optimal" choice. 28 is hardly an "old" age to become a father.
I do take issue with the statement that young people (people in their 20s) have energy "in abundance."
As a dad to 2 kids (became a father at 28) I would strongly urge people to wait until they were 30-38 before having kids.
Given the great innovations in this space I'd even say 40 is a great age to have kids - though it gets harder with age beyond this imho.