I had a free subscription to pretty much every magazine that was carried at the check out lanes. It wasn't so I would become a fan of a title, but that 'free' subscriptions still count for circulation numbers for advertising purposes.

The industry gave out tens of thousands of free subscriptions to people like me, because each one counted as 1/3 of a paid subscription for this type of reporting. 

My point is, every industry finds ways to 'enhance' the count of their user population. Twitter is just the modern version of what the industry has done for decades.

N.B. It still would be nice if the fake accounts got cleaned up, but I am not holding my breath.