Why is "my faith in humanity is restored" the response to a good deed?

[TheDude]

Whatever happened to thank you?

It is kind of annoying to me and yes this is a bit of a rant. If I were to put a definition in Urban Dictionary it would go something like this: "Anyone who uses social media (i.e. Reddit, Twitter, Instagram, Facebook anything on the Internet) to excess to a point where they actually believe there are no good people out there."

For example,

"Bro some old lady held the door open for me. Faith in humanity restored!"
"The homeless man gave me 25 cents for a change (pun intended)! #faithinhumanityrestored"
"Dude I punched a guy and he said sorry to me! My faith in humanity is restored!"

Honestly, there are amazing/good people out there. Our media chooses to be 95% negative and put negative twists on everything because conflict and tragedy are "more interesting". I understand that my words mean nothing and the only person I can change/control is myself. I also understand that other people have probably said the same thing in a different manner. I just want it to be documented that I said the same thing and hopefully this can stimulate some discussion.

Thoughts?