I wonder if there is bias there in the moment in time chosen. Having been a genX young professional in 2000, my impression at the time was that the rocketing Internet bubble caused a lot of people to switch jobs much faster than they had done even just five years earlier (lots of Internet companies were recruiting heavily and plucking people out of other jobs because the demand for new hires was so high. Lots of rapidly growing companies with stock options to offer made for an employees' market). After the bubble collapsed, jobs were much harder to come by, which in turn meant job tenures were longer. It would be interesting to compare today to 1997 or 2007, rather than 2000.
"As of January 2016, the typical U.S. worker had been in their current job for 4.2 years, up from 3.5 years in 1983, per the Bureau of Labor Statistics."
There has been a significant slowdown in the speed at which people are changing jobs.
Younger people today are also not showing any indication of switching jobs more frequently than in the past:
"Millennial workers are as likely to stay with their current employers as members of Generation X were when they were young adults back in 2000, according to a report released this week by the Pew Research Center, a nonprofit think-tank based in Washington, D.C. Roughly 63% of millennial had been with their employer 13 months or more as of last years, versus 60% of Generation-Xers in 2000. Additionally, a fifth of millennials have been with their company for five years or longer, again in line with Generation X."
[1] https://www.bizjournals.com/sacramento/news/2012/12/27/how-l...
[2] http://www.marketwatch.com/story/young-americans-stay-in-job...