If you don't pigtail, when you have a problem with a plug, then all plugs downstream are done.....in Canada, it's a code rule that you have to pigtail, so you don't interupt anthing down stream if you have to work on something. Here is another reason that i have been seeing lateley, if you check the push in's 2 or 3 years down the road, the mechanical mechanism loosens up over time and you start to get arching and sparking.....not good. Especially in my house.
