I don't think this is a necessity but rather a trend bourn of hardening rituals and habits. When you're young flexibility is built in, you are moving quickly between milestones and change is part of the program, thus your adaptability is high which provides softer cushions and greater perceived rewards for change and growth. But as people begin to settle on a solid self-identity, holding fast to the place in the world they think they've carved out, this adaptability wanes and change starts to become more disruptive.

But of course this need not be the case. At 30 you have even more life direction choices available to you than when you were 18, indeed given this forum it's difficult to even fathom how many there truly are, though I'd wager you felt like the future was a lot more open when you were 18. But that's just inertia you're feeling, not destiny, and it can be changed at your whim.

Of course the WEIRD caveats apply here, as well as a host of other generalizations and psychological needs I'm glossing over. Nonetheless hopefully the shape of the point I'm trying to make finds some purchase.

I mean, just on the physical front one is not able to do things they used to and require more medical attention. That brings with it financial costs, dealing with broken systems, etc.

Yes physical is one of the things I glossed over and generalized, and of course there is real physical decline that is inevitable. However most people are not genetically destined to be saddled w/ medical bills immediately following their peak, and with basic self-care can maintain general freedom to adapt and move about several decades beyond yours (seems about 60s or so is where you'll likely experience issues of some sort even if you're in exceptional health).

Of course again the trend is that many people don't exert said self-care and fall subject to ailments much earlier (or just have bad luck w/ a host of varying types of environmental/genetic circumstances), and just generally use getting older as an excuse to withhold themselves from a great many things. This again is not destiny, merely a trendline that can be changed.

I am going to lightly disagree with you :-). I think it is absolutely true that our future lives are the product of our past decisions, but "problems" (or challenges) can sometimes lead to better forward thinking.

As an engineer I know so many people who were the first in their family to have "lots" of money and they chose to spend it as if it would always be there, until it wasn't. Their challenges in adapting or supporting a burn rate that was unsustainable, could be directly traced back to their choice to live "beyond their means" as we say, which is to say spending all the money they were making and saving none in case of an issue later.

I was lucky (and there is tremendous randomness to life) to marry someone while I was young who was much more fiscally conservative than I was. As a result of that, I was able to experience times when she had insisted on saving and it turned a "bad situation" into a "manageable" one. People I knew and worked with had less pleasant outcomes.

Today, it feels like (although I don't know if it actually is true) that the whole "getting married" thing is out of favor. And yet being married and having two people who could work so at least one of us was providing employee provided medical benefits etc, kept "calamitous downturns" (which happen regularly in Silicon Valley) from feeling like the end of the world.

So I look back and see the choice I made to get married early as a choice that provided a mitigation of the negative impacts of events that happened after I got married. In terms of bad choices, when the dot com boom was in full swing I had stocks that I could have sold and paid off my house mortgage. I chose not to, yes explicitly thought about it and said to myself, "nope." I only saw the down side of that choice of incurring a bunch of taxes, and hey I was making the payments easily on my current salary and so I deferred.

Then when the crash came and the company where I was working was evaporating around me as its customers were filing chapter 7 bankruptcies, I was looking at finding a new job and still having a mortgage that my now GREATLY devalued tech stocks would pay down but certainly wouldn't retire that debt. Ageism is definitely real in the valley and I was concerned I wouldn't be able to find a new job, would have this mortgage and a family to support, and would end up taking any job I could find just to survive, or selling the house and relocating to somewhere where the cost of living was once again within my means.

The hardest thing for me is being honest with myself and really looking at how and why I chose the way I do. I find I can convince myself that the decision I want to make is the right one, even when there is clear evidence that it is not the better choice in terms of mitigating future risk. Being burned a few times has helped train me to listen to those warning signs.