Numerous reasons. I used to play like 10 games a day , now I play 1 or 2 games every two or three days.
One of the reasons is the way the game is heading. I loved beta, I changed dota and lol for HotS because it was different. Shared experiences, no items, tower ammo, talents to counter-pick enemy choices, numerous path builds, specialists, and so on.
Slowly the game changed into something I don’t like that much anymore. Forced e-sports, changed to experience gain, map layout, heroes, talent trees, removal of ammo, third tower, specialists… Everything I liked is being slowly removed, reworked, changed. Like last role reclassification. Tell me again, what was wrong on specialists? Because Probius is totally range assassin comparable to Zuljin or KaelThas. The game now is not the game I wanted and started to play.
Second reason is the abuse-able reporting system. I won’t say I never exploded and was not toxic. I was. Yes I was also silenced and I deserved that. At least two of my silences were not justified, where the GM kept the silence after providing me one weak proof, because he couldn’t find anything. But I said screw it and turned the allchat off.
But something I never ever done was giving up, afk or so. Yes, my favorite hero is Abathur. But getting notifications about being afk/nonparticipate in the game with probability of getting banned did lower the number of games played. You know that the reporting system is not working when you experience it yourself.
And as last, but not least, it is the matchmaking. Since I remember, it was bad. Full of promises, 0 real solutions. No changes over the years to make it better, 2017 december screw-up with the placing, where I had to make the placements THREE times, yet ended up 9 ranks below where I was. Managed to climb back, but it was so painful that I never ever will do that again. If they place me low again, ranked is forever over for me.
Oh, and add the last merge of TL and HL into storm league, where they took the higher rank. So mostly from TL, where 80% of players were placed wrong. And they did not even add the “play solo” button they promised…