Yep. And you need that, becuase your website, that cotains maybe 1kB of useful info (eg. news article), now needs to transfer tens of megabytes of random garbag

Yep. And you need that, becuase your website, that cotains maybe 1kB of useful info (eg. news article), now needs to transfer tens of megabytes of random garbage, needs you to connect to 50 different external services, and where a simple even a basic share button, that could be implemented with an 'a href' pointing to "http: //twitter.com/share/?url=http....", now needs 3rd party cookies and external resources to track your users. So in a real-life example, this is like a movie-ticket seller optimizing the ball bearings in a shopping cart that you need to buy those tickets, because they want you to carry a bunch of flyers and gps trackers with you, while all you need is a small paper ticket.