Or other games, in general. 5000+ hours in total. Seriously, why though?
Before the story, let me first tell you what I'm going to say in the following : to stay connected with a small circle of friends without the usage of any social media and to exhaust my brain so that I can sleep.
I was born in the early 90’s. That meant for me landlines to call people, hardcover encyclopedias to prepare school projects, going out to play or socialize with the kids from the neighborhood, and an old computer with no internet access (we've got it a few years later) that I can barely install and play one or two games. Only a few games, but I loved them each and all.
I'd be looking forward for the Friday afternoons where I came back from the school and basically was allowed to spend an extra few hours on the computer to play whatever game I had at that time. The excitement would start from the Thursday night when I realize that it's Friday tomorrow. Then it'd be the Friday afternoon and I'd be rushing to the computer sometimes even without changing my school uniform. After that, it was magical and time would fly by while I commanded my tiny armies to victory or ruled my small village to a metropolitan city. I've kept this joy for my entire life, including now.
Growing up brought more school work and less free time for my hobby of playing computer. Within time, especially from high-school onwards, playing computer games became a hobby that I can only do in the summer or winter breaks and maybe during an exceptionally lazy/empty week. I just had so many other commitments that I didn't have time for playing. Again, though, I'd be looking forward for the school breaks, just as I did for the Friday afternoons, and these times I'd be playing for entire weeks, not only during an afternoon. For me, it was the routine that I'd be spending the first week of the school/university break in my room, kinda isolated from everyone and everything else, just playing whatever games that I was favoring at that time. That was my rehab.
After I graduated from my bachelors, I moved away from my hometown and relocated within the country. That was the first time in my life when I was indefinitely away and far from my friend circle. Sure, I managed to form new friendships but none of them were like the ones I had and yet having more friends does not mean that you miss your others. This is the first reason why I kept playing Dota 2, which I was introduced around my master's work by my flatmates. That's how I figured out, although pretty late, that I can summon my old friends around the game, who were already playing it without my knowing at that time.
Gathering with the friends around the game continued and even escalated more after I relocated for my PhD to a foreign country. There I was, at least initially, totally alone and missing more and more of my friends. There, playing the Dota 2 become my the most sought activity. Most of the times, I'd clear anything that I might have been invited for in the evenings out and sit down to play, for hours and hours, with my friends. Of course, it wasn't only the playing itself that entertained me but as we spent time in front of the computer we were talking about anything that might be interesting in our lives, our problems, or sometimes straight bullshit fun. Gathering these people for a normal chat in Skype or whatever is rather impossible: none of us would have agreed to come if one had send us a Skype meeting. But for the game and the conversation around it, everyone was there.
There's another side of this story. I didn't have a particularly happy, successful, and interesting PhD. Things started getting busier, stuff started not working, the dissertation and defense dates kept getting closer and closer. In the end, I was overwhelmed and some say, in a rather bad psychological state. Insomnia and constant worrying were my new companions. As I couldn't find another way to not to think and worry, I immersed myself more and more into the game. It was not only my rehab but my safe house as well. I'd be playing until I was mentally exhausted so that I can just sleep. That kept going on for 1.5 years. Did it help with my PhD? I don't know, but playing, especially thanks to my friends, kept me saner than I'd be otherwise. By the time I reached the end of my PhD, within 3.5 years, I had accumulated almost 4k hours in the game (for those who might be wondering, I still suck pretty hard in it).
After all these years, I am still playing though for more moderate durations. Why is it Dota 2 but not something else? This is here irrelevant. But it kept me connected with my friends and provided some sort of escape when I couldn't find it physically. It's still connecting me with my friends and still offering me fun and joy after those long hours of work.