Liar liar pants on fire...

Why do people take the time to write fake stories? A beautiful picture of a dog or kid that they find on the internet and they use it to write a horribly sad story.
Examples,
The guy in the army that dies and his dog was put in a shelter by him and said only if he died give his dog for adoption. The person that adopted the dog posted his story and added the letter from the dead officer. The image of the dog its taken out from a magazine.
The dog that had blood and the woman that thought her dog ate/killed her child and she killed the dog by punching him. Then she sees the child safe in another area in the room and next to the blood it was a dead snake. She wrote she was sorry for her action and not to judge before seeing the entire thing.

For the soldier I cry for both dog and the dead soldier.
For the hero dog that kill a snake to protect the child from harm and he still died by the hands of his owner (woman.) I can only say I cried for the dog and I only have hate for the woman.

Here is my thing why do people write fake letters, put sad quotes on pictures.
Why write a false story about a picture in that family that he / she knows nothing about.