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.