I get where you're coming from and hadn't really thought on that aspect explicitly yet, but my first thought is that rather I'm missing half of the journey that I want to have.
To torture a metaphor, I like hiking, my wife and I have a goal of hiking the whole SHT [1] in bits and pieces over the course of 5 years. We've found parts of the trail that are absolutely amazing to hike, we could just hike those sames bits over and over again because we know that they're amazing and not risk having to hike the bits that are just a mowed bit of grassland (which is uninteresting to hike), but then we'd be missing out on the whole experiance and not only that we might be missing out on even better sections that we haven't encountered yet.
I feel the same way about how I'm progressing in my career. I could keep doing the same bit over and over again and I'd probably be pretty damn good at it, but I just can't let myself. I'd rather keep exploring, keep experiencing not only what's new, but what's old-hat to others but new to me, and see if there's something out there that I'm even better at that I enjoy even more than what I already know.
[1] https://shta.org