hahahaha that's quite an interesting perspective.
Perhaps they don't do so to prove their existence, though, so much as to convince others that they exist in an attempt to satisfy their ever-growing insecurities. They want to be seen and heard. It's a very interesting phenomenon, actually. Why do these people need such reassurance as to their own importance?
In our century, compared to very early humans, there is little to distinguish you from anyone else. You're just another yuppie. Or maybe just another scene kid, soccer mom, stoner, intellectual, runner, alcoholic, whatever. Such was not the case when humans were confined to small groups. In a village, everyone knows everyone else. Your importance is grounded in your relationships with the people around you. There isn't much of that anymore because those sorts of strong experiential relationships can be used as leverage against others due to the extreme connectedness of our time, and, thus, fewer strong relationships actually persist. When fewer stronger relationships persist, you have to make up for it with many more weak relationships. The best way to do this is to advertise the shit out of yourself. Everyone knows who Paris Hilton is (take that sentence with a grain of salt). This is because she has the resources to advertise herself. I'm sorry to bring up Paris Hilton, but she's just such a representative extreme.
I don't pretend to have a strong understanding of this sort of action. I haven't thought about it nearly enough to be able to articulate anything that I can really support, but these are views that I thought may be worth sharing. I'm just going to continue writing vaguely when I start to write vaguely. If that's not okay, let me know.