why fb is created by its owner ?

Mark Zuckerberg started with the idea that Facebook would be useful to his fellow students. He specifically did NOT think of how much money he might make from it. If your main reason for wanting to make a website is "to make money", then you are already thinking the wrong way. If you want to merely copy someone else's idea, then you will have to be at least as intelligent and as skilled as Zuckerberg and his group of friends who designed and coded the idea and will also need to have that 'one in several million' lucky chance which makes your site actually wanted by millions of users.

watch the movie "the social network" that movie is the life of facebook creator,.