Learning involves being wrong, and being wrong is stressful. The older you are, the more stressful it is. In humans, there is a strong ego component, but I imagine that there is also a physiological resistance that comes from a lifetime of learned skills, models, behaviors, and traumas. Having gotten cuts, scrapes, bruises, and maybe breaks while learning to ride a bicycle, which still continues to work just fine for getting you where you need to go, it's a hard sell to suffer or risk another set of cuts/scrapes/breaks to learn to ride a bikeprime, even if it's a qualitatively better tool--it's not essential. And we also learn over the decades that our bodies and minds at 64 are not as flexible and resilient as they were at 4 or 34.

If there were just one new bikeprime every few years, it would be easier to settle in for the pain and benefit. But the pace of technological change is much much faster, and along with intense marketing, it seems like there are dozens of new bikeprimes every year. Many of these turn out to be mostly hype, so it's hard to know where to invest energy. And every time a supposed bikeprime turns out to be more pain than it's worth, there's a real lesson that's learned about the value of bikeprimes in general. And so we become older, more skeptical, more rigid.

I also think there is some aspect of survivorship bias in the value of "learning new skills". For every person who invested the time in learning a skill that turned out to be valuable for them overall, there are other people who spent years investing in a skill that turned out to be a dead-end.