Does the privacy on the Internet exist? And if it does, do we really need it?

Nowadays, when the Internet is so wide spread, that we can’t live without it, the issue of privacy on the Internet is extremely important. An average internet user supposes, that nobody can use his personal data except posted by himself in the social networks. However, it’s completely not true. Your provider can get all your User History, majority of sites use cookies, that collect information about you, your interests, purchases, friends etc., your phone collects information about your movements – we can continue this list for a long time. So, the only way to maintain privacy is not to use the internet at all (of course, you can try to use TOR browser, but even it isn’t completely anonymous, as its creators claim). 

But the problem is – do we really need anonymity and privacy on the Internet? Of course, random people shouldn’t get your personal data (just don’t post a lot about yourself), but analysis of your data (big data analysis) by such companies, as Google, Facebook or Amazon can really improve your activity on the Internet – they can advise you, what to buy, which film to watch, find more relevant information for you in a search engine, and so on. And the more data is received, the better are mechanism for analyzing it – the greater our life can be. As the founder of Google said, the Internet will soon be everywhere. So, maybe it really can really our life?
But, there is another questions – to which extent can companies use our data? Who has access to it? Should the law at all admit it? If all this aspects are mentioned in the law, in my opinion, they could do it, because, if it's improving our activity on the internet now, why can't it improve our life in future?