Conpanies like Facebook, apple and google have reputations to maintain and if they give out your personal information in ways you have not agreed to they will suffer financially.
No they won't. Facebook gave millions of users' data to Cambridge Analytica. They were fined $500,000, which is chump change to Facebook. Google Plus revealed that 438 different third party apps had unauthorized access to your data. No punishment. Similarly, Apple have plenty of third party apps which sell your data. No punishment. And that's only if you think that these companies aren't selling your data themselves, which I find very difficult to believe.
I am not sure what government fines have to do with anything. After the Cambridge Analytica scandal, Facebook lost over $130 billion in market value, however they recovered after implementing changes to prevent this from happening again -- and the outrage was more about the fact it marginally helped the Trump campaign than the amount/type of data leaked IMO (it was mostly public information, but in mass quantity not easily available to the public). The Google plus data leak was the result of mistakes in regards to data security, and not malicious intent -- anyone who stores data is going to have the potential for leaking data, I am also not sure what data Google Plus has, but I would presume it would not be much more than what is shared with connections, but may not be public.
If these companies repeatedly misuse and/or mishandle customers' data, their customers will not give this data in the future, and advertisers may not want to advertise on their platforms.
Over the weekend, Zuckerberg wrote an
editorial in the Washington Post arguing for more internet regulation so he can hide behind the regulations (and blame the government) the next time he has a similar screwup.