They also contravene Rockstar's terms and conditions, so pursuing that route risks getting your account banned. Rockstar already offer you the chance to pay real money to add cash to your Online account, so an official money cheat will just never happen. These third-party initiatives, that tend to ask for your Social Club information and have you take a survey, are scams that must be avoided.
However, if you're here looking for a GTA Online money cheat, they exist, but they're not worth the risk. The single player stock market persists in all instances of the game, and it'd be ruined if any player can cheat their way to their fortunes in an instant. That's down to the game's stock market, which is one way of ensuring that you can still lord your many millions over the rest of Los Santos from your glistening ivory tower regardless.