The final straw for me was actually a girl from my elementary school who wanted to friend me. The chat went like this...
Me: I have to ask you something. So we haven't seen each other for decades, the last time being when we were 7 year olds. Back then we probably exchanged less than 100 words. I don't mean to be rude but I'm genuinely curious to know why you want to connect with me?
Her: Oh I'm sorry. Didn't mean to offend
And that was it. She didn't have a reason other than "just because". That was when it really clicked for me what an utter waste of time Facebook actually is.
Never looked back