It's hard to just do it to test the waters when you have a technical project and multiple interviewing rounds (which also include live coding, which for me is very stressful).
But also: I like change. I notice I'm more productive in the first half year on a project. Almost every project is interesting at first. Not all projects are still interesting after a year or two. When I get bored, I know it's time to move on. Some companies may have enough diversity in work, and enough flexibility to move me around, that can keep growing without quitting, but my experience is that most don't.
But I'm not constantly job hunting; as long as I'm enjoying myself, I tend to ignore other offers.
This also gets more extreme with stock appreciation because the first grant being the largest is also the oldest so has the most time to appreciate in value. Me for example, the value of my vesting equity per year will drop 30% once I hit my cliff next year.