And it's the American way of doing business. American people and business do whatever they like until there is some law created and enforced on their situation by the court. As long the court doesn't say you aren't allowed to do it, you can keep continue doing it. If the court told 1 pap to stop, the other papz are like "The court didn't told me to stop.".
In Europe it's the opposite, we check the law first before doing something and most of the time we just don't even bother to start doing something. This means that the big brands are American, there is no European Microsoft, Apple, Facebook, Twitter, eBay, Amazon,...
Oh and one more thing, that paragraph doesn't apply to arrogant celebrities who post red carpet and random paparazzi pictures of themselves on instagram (Kardashians, Rihanna... I like her but also Beyoncé). Not only is that so disgustingly vein but I'm not in the slightest bit sympathetic towards those people in any situation with paparazzi as they obviously love having their picture taken for them wherever they go.
Some celebs are doing it for publicity, keeping up their relevance by calling the paparazzi before exiting their house.