If somebody won against you with a particularly dirty strategy you can get back at him and you won't be fooled the next time.
It's better than dota system where you're most likely never going to play vs the same people again (or at least it feels like that).
Also the whole 5v5 game that lasts for 1 hour format is inherently very toxic - most of the time you know you lost after 10 minutes and yet you can't disconnect and have to keep playing for the next 30-50 minutes while everybody blames everybody else on your team.
In sc2 if you know you lost after 5 minutes it's discrespectful to continue playing :)