Because I am addicted to the Internet and utilize it as a crutch for my total wellness. Working graveyards is very isolating and lonely. Sometimes I wake up, go to work, come home, wait to go back to work and throughout maybe i talk to 5 people; little hollow "Good mornings" and "Sure is cold." etc. Sometimes less. Communication is a fundamental human need and without it you become spiritually diseased and i find myself spending exorbitant amounts of time awaiting the next interaction here, far mre than fillyacup. Also, propping encourages people to post more because it's a positive form of acknowledgement / validation, and makes people feel appreciated and supported. Also, the act of pressing the button and seeing it light up and then seeing it on the page is conducive to small releases of dopamine in the reward centers of my brain and I find it to be nice.
These are some reasons why i prop more than more fillyacup.