Online registration is mainly used by vendors as an anti-piracy measure. It also enables you to play online against other players. For some titles, it’s also necessary for installation – in Half Life 2, for example, a web connection is needed to decrypt and install the game contents on the disc. Data-privacy laws are stringent – provided that you opt out of marketing emails and the chance to create an online profile, your details won’t be shared by the vendor. There’s no getting around the need to register if you wish to play these games.”]
Source: https://www.csoonline.com/article/2127711/how-to-protect-your-data-when-registering-online.html