Hi I’m fairly new to the game and am only bronze in comp. I’m confused though because when people leave I get punished and my SR drops, substantially. I tend to go up 20-25 SR for a win. In a game I just played we were winning, I had a 15 players kill streak, no deaths. We win the first round. Then someone leaves and it’s now 5v6 and we lose the second round. Third round comes and we get pummeled. My SR drops 20! Why does it drop the same amount I gain when I win? Shouldn’t I be rewarded for winning at all? I understand the whole reason why the team would still get a lose I guess because a group could just have someone bite the bullet and leave so everyone elses SR stays in tact. But at this point I don’t think SR should be hurt that badly. I dunno I just get frustrated because I feel like I am doing so good and then this happens and I never leave bronze. Sorry for the long post
If you are not a leaver yourself, there are six chances for a leaver on the other team, and five chances for a leaver on your team, so you will gain, overall, over many games played.
Blizzard does not adjust for leavers because it can cause perverse incentives. “We’re losing, let’s report this schmuck unless he leaves to save us from losing SR!”.
For more, see How Competitive Skill Rating Works (Season 12) → Leaver Penalty. The references give Blizzard’s statements on the topic.
The chance of the other team will leave is very low though. You could win with 5 vs 6 but rarely happen. Overall, just deal with it. They would not fix this SR problem. If they want to fix it, they would do it long time ago. So just enjoy the game 
Pad your stats the best you can so you lose less sr. Sometimes this isn’t possible and you end up spawn trapped, sometimes you win a 5v6. Most of the time you just forget your stagger fest of a team and try to get your stats up.