The fact is that the PKK are mainly non-Syrians and they control a vast area full of non-Kurds.
PKK doesn't control territory inside of Syria since The undeclared war.
People who only put up with them because ISIS and the rebels are even worse.
That's the only reason why people put up with the Regime.
While the PKK's cult like behaviour, Kurdish nationalism and their habit of monopolising everything and disenfranchising locals always has them stand out.
How does PKK matter for Syria?
When Idlib, Ghouta, Homs, Qalamoun , Deir Ez Zor and Daraa are sorted out the government will have the upper hand. Instead of having the best part of their army split into small units to shore up conscripts. They would be able to use the Republican Guards, 4th Division, Tiger forces and Desert Hawks in their full form.
Yes, then they will take Golan Heights, Ankara and Riyadh. After the Rebels are defeated SAA will be in it's worst state yet and it will have to deal with an insurgency.
The PKK hasn't shown any ability to engage in multiple simultaneous offensives nor do they have the logistics to sustain it. They don't have airpower, mechanised units, intelligence services and local support that the government does.
And how does PKK matter for Syria?
Their only hope for keeping all of those areas is if Damascus in the future is either hobbled by a deal with rebels that cripples them or decides to let Kurds run those areas.
Keeping? PKK doesn't control any part of Syria.
Considering how the PKK has behaved that won't happen.
I don't think PKK had any relations with the Regime for over 2 decades.