Because ad tracking is all about reach. I use ad-blocking, but maybe 80% of my Facebook friends or Twitter followers don't. When I share an article, there are p

Because ad tracking is all about reach. I use ad-blocking, but maybe 80% of my Facebook friends or Twitter followers don't. When I share an article, there are potentially 80% of my acquaintances who would see ads. If I never share it because I couldn't read it, there is zero potential.