Because they play identity politics. They learned their ADQ lesson well Anyone remember Hérouxville? Where do you think this "Charter of Values" comes from?
That's the problem, Quebec is becoming a Hérouxville, on a much larger scale.
It seems like PQ members are so confident to win the elections that they did not bother to hang their signs in the streets (well at least in some areas of Montreal). I saw mostly big signs of Québec Solidaire and some little signs promoting PL candidates.
It is annoying and expensive to go to vote every 18 months, but it is very important to do it.