How GPC works? I'm understanding that it send "signal" to not sell my data, is it true?
Because it doesn't make sense for me. Why I must opt-out from selling my data? It should be exactly opposite, otherwise it don't make any difference. And why it is acceptable on the Internet? In the world outside the Internet nobody would agree on stalking and selling data as default...
Opt-out is more profitable than opt-in. If adtech had to make do with opt-in, it would starve to death for lack of data because most people make do with the default option and—as you pointed out—most people don't want to be stalked or to have their data rented out to every corporation that wants to send them an unsolicited sales pitch.
Also, opt-in is the advertising equivalent of self-reporting in polling. You're not getting a representative sample of the population.
I know but so what? It's not "protecting my privacy" if it's opt-in by default...