Opera specifically is owned by a loan shark company; avoid that shit even if you're a member of the CCP itself.
Why would you not want your data to be sold in general? Because it'd lead to your internet experience being less private. Companies can buy your data to give you targeted content while you're browsing the internet and it could influence you all sorts of ways from giving you the idea to buy a product, to showing you a specific political candidate's propaganda during elections; which does literally influence another country.
In my country; all the retro consoles (up to playstation) are called atari.