Why do people expect personal information about you?

I don't understand that ether. If they want "live" interaction they can just go out. But they want your name, town, how old are you, your mail, messenger and photo. And not only the opposite gender, witch i would call stupid, but the same gender people as well want all this info. I once know a girl who asked for a photo 12 times. And the thing is - the other people gave her all that. And thought I was the strange one not wanting to share personal information with a stranger. What are they thinking? Is that that they are maybe real young? How can they gave their photo - what if that girl used it for some adult sites ??? Or in other way? I don't understand, and i get real awkward when they start to complain. I wonder what others do. Do they give out real info? The only friend that I gave info one time, i was young, declared that he is coming to see me in summer. how would i explained that then? mom, this stranger, who i only know from mails, is coming to stay in our home for summer? And he got offended when i told him not too. Sure he was nice, we read the same books, have the same interests, but that's not enough. It's internet, ffs. And I wonder now, what he would have said if i had said, no, i will come to your home. Somehow i don't thing he would have agreed too. We lived in dif countries by the way. Now i never do that.

Yes you are correct people want messenger or phone number without setting trust or nice friendly contact and they are scam. Someone want to sell you something for which want messenger. Seeking phone number for sending text or pic may be but it is not fair to ask personal information too quickly without setting any trust. Some site's affiliate or agent also want messenger's id. Of course, in some cases some simple minded people asked for messenger or other contact number reading your profile's interest thinking that you will be interested in chatting. I do not want any one's personal information without setting any good relationship.