Why any player leaves Eve Online (whether for a while or forever) is a question that has no definitive answer. It largely depends on the individual who is leaving. This means I have to look at the demographics of Eve Online.
Here is a video of Historical Player Age Distribution over the course of an entire decade (2003-2014).
The median age starts off at 26 with the highest percentage being about 24 years of age in 2003. At the end, it shows the median at 31 with the highest percentage being between 26-29 years of age.
Unfortunately this doesn’t give us the complete picture. But I can deduce from social media as well as from how everyone talks around here and the kind of personalities that are popular around the Eve Online community that a sizeable chunk of the demographic are grown men and women who have families and careers. We know at least one of them works at NASA. Some of the others around here are engineers. Some are programmers as well as masters of spreasheets. Only a handful of us around here are dedicated streamers like Manic Velocity, Wingspan TT and Zarvox. As for me, I’m an aircraft mechanic.
The rest of us, I don’t know.
Based on what I can find, the only logical conclusion I can draw is that many players who leave Eve Online are not likely leaving because of the game but because of real life obligations. After all, Eve Online is only a game. Although this doesn’t mean that anyone who leaves is leaving because of that. There are admittedly players who leave because they found out the hard way that Eve Online is the most cutthroat MMO in the entire industry and that just because you bought something expensive with your credit card doesn’t mean it’s yours forever.