Why is it that when someone met you and learned your name, their first instinct is to add you on facebook?

I went to a church recently and met some people there. I gave them my number, so technically, they can use that to contact me if they really want to.

And yet I still received a facebook friend request and an urge from a fellow acquaintance asking if I have accepted the person's friend request.
Like for what?

People normally just stalk you there, look at pics and achievements and stuff. And here I am trying to make friends with strangers without looking at their credentials.

Thing is, I know what looks good on credentials and what not. I do not want people to like me just based on that. I just want to be seen as me.

So now I am rethinking if I should keep interacting with those people or not. I just found the fact that they had to use an acquaintance to get me to accept the request a red flag. But mom said it'd be rude if I turn it down.

Personally, I really don't want to. I am alright to speak and meet with them already and asked the fellow acquaintance to relay it to them. But I don't feel comfortable accepting the request of someone I only just met who even had to go through such length.

Advice?