Disneyland is a different sort of beast.
Their 'on-site' resort capacity is really extremely small (three hotel options) compared to the capacity at WDW (20-odd full-scale resorts). They use what are called 'Good Neighbor' hotels to increase their package-booking ability - you choose whether you want to stay in one of the actual Disney hotels or in a Good Neighbor hotel when you book your package. The Good Neighbor hotels are not owned or operated by Disney, they just happen to be nearby and participate in the package program.
Their dining options are fewer, as well. They do not have the resorts where many of the WDW restaurants are operating, after all. There are only the two parks and the Downtown Disney area, not four full-size parks and the larger Downtown Disney area that are at WDW. There is nothing like Epcot, where there is a huge park with a lagoon lined with restaurants.
And so, since PINS generally have to do either with an on-site resort room discount (i.e., 40% off a deluxe room) or with the dining plan (which does not apply in Disneyland), they are not suited to Disneyland bookings. Instead, they offer package discounts and such to the general public - with a smaller on-site capacity they have less problems meeting occupancy goals.