Another reason people job hop is that many tech companies have an annual round of layoffs where some segment of the workforce will be laid off. Women, people of color, and opinionated people (especially opinionated women and poc) tend to be first in line to be laid off. So it might not be a choice to job hop if you're one of these people.

It IS possible to be good at learning new technologies and environments, acquiring depth in just a few months. In this case, job-hoppers will be both wide and deep. They can be exactly what companies need where most of the people have ever seen 1-2 workplaces and don't have a broader insight into the industry.