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 :)
Sadly in a team game you can't make that choice because disconnecting too much will prevent you from playing all the fun modes (and will put you into a low priority queue where you play with people who constantly insult everybody or kill their own allies).
That's the root cause of all the toxicity in dota.
The chance that the enemy throws a fight or makes other mistakes that opens up new win conditions (or sometimes that simply one guy in the other team tilts and throws) is just too high in Dota in order to be able to call it quits after 10 minutes.
One of the main reasons for the toxicity in Dota in my opinion is that people don't understand that there are 10 variables in the field, but they can only control one of them. Don't even bother trying to influence the other 9 (apart from positive feedback/encouragement/communication to the team), it's a waste of time and only contributes to the toxicity.
At this level with the same position and firstpicking ww I get a small subset of heroes I play with and against, so it's much easier to call. I have pudge and sniper every other game for example, and enemy pos 5 is very often cm or ogre :) It's a great day I get to play vs meepo or oracle but it almost never happens. The best I can hope for is axe or legion.
Also half the fancy strats don't work because people don't talk. Split-pushing is just split-feeding. Nobody does 3-lanes. Jungling is a last resort of carry that lost the lane and when he's fat the barracks are already destroyed.
So if we lost laning hard enough and have earlier-game cores than the enemy - we lost, it just takes a lot of time to play out.
But even if I was wrong 30% of the time instead of 1o% - I'd still happily take that trade in mmr if I could. Obviously pro players have different motivation so for them it's "never surrender", but almost nobody is a pro.
More importantly, though, your MMR has now been split up across the three factions that you can play as. If your Terran gameplay is much better than your Zerg gameplay, you'll be facing higher-ranked opponents when you play Terran, than when you play Zerg.
This has made it easier for players to switch their factions up, without being punished for it.