For some people it's not having enough time or a desire to do other things, for others it is a lose of passion. It's not just the digital era, and this article isn't just limited to video games.
For my entire life I was a bowler (see: bowling). From the time I was eight, until roughly 19.5 years old. I'm not talking going once every month or so with friends to have a good time with it. I'm talking a minimum of two times a week, multiple hours sessions, typically with a coach or one other competent friend. This was a routine for about 12 years. It was more than a passion, it was life. It was an ingrained part of what it meant to be myself. With that came a lot of physical and mental anguish, a lot of friendships, trophies, some local records during high school, and other accolades. A search of my name would likely reveal a lot of bowling related things.
Fast forward to college:
I continue with bowling at a higher level than ever before - collegiately Again, multiple practices a week in a small setting with great coaches. Tons of travel, national competitions, you name it. But then something happened. I got burnt out. It's worth noting that for a long time this wasn't something that was particularly fun, but I got addicted to the competition - the thrill of it, the feeling of winning and knowing that you're great at something. But it still happened, I still got burnt out after a full year of this in college. How did this happen? Eventually it got to the point where I accepted that I would never be as good as some of the people out there, sure. But moreso it was the opening of other interests while in college. A whole new world arrived and has been a mostly rewarding since then. New activities, new interests, and one less competition to worry about. I still don't go bowling with friends though, it's not something that I can handle.
Losing passion for something you love can be a part of life. This article applies it to video games, but it can applied to anyone and anything. It can be physical, it can be digital, it can be emotional, anything. Life is a constant change, to apply some engineering jargon here, steady state is never reached. Losing and gaining passions is part of that.