My thoughts are after almost a decade of growth, the popular opinion (right or wrong) is we are due for a market correction. I think that these companies want to cash out at the top of the curve.
Take a look at the 10 year S&P 500 chart:
http://www.macrotrends.net/2488/sp500-10-year-daily-chart
It bottomed out in early March 2009. The period from March 2009 to right now can roughly be described as "growth." We describe it as "growth" because the overall movement is upwards. 9 years and 1 month is "almost a decade" because a decade is 10 years and 9 is pretty close to 10.