One reason is that people generally expect large companies to have a level of scrutiny and process associated with collecting that data, and reasonably trust th

One reason is that people generally expect large companies to have a level of scrutiny and process associated with collecting that data, and reasonably trust that it won't be used "improperly." That trust does not extend to "some random guy" hijacking those companies' systems. The other reason is more visceral, in the fact that those photos of themselves and others were displayed semi-publicly. A lot of the tracking that goes on is invisible if you don't think too hard about it (out of sight, out of mind). If they saw a dump of a bunch of people's private messages or search history (even anonymized) posted online for anyone to see, they would likely be similarly spooked.