It’s been a while since the forum hasn’t been submerged by a sea of PtP threads. As you’ll see, it’s a polarizing subject 
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I had this to say last time (micro pay-walls).
In short, it’s simply to allow to set a price on any piece of public content. The price needs to be paid before the data can be downloaded.
It won’t stop pirating content, but if the price is fair and the process simple, it wouldn’t need to.