People who drop spoilers

People who drop spoilers casually, why do you do it?? And I'm not talking about people who put spoiler warnings and are respectful about it, but those people that just drop major events in random posts like????
As someone who hates spoilers so much that I don't watch trailers and the text on the back of a book (can't find the English word, sorry) I want you to know I despise you. I loathe you.
You're ruining the experience for people. Why? Are you just a shitty person or are you too stupid to realize that people out there don't possess the same knowledge you do?

There is a way to handle spoilers and I can appreciate them myself sometimes as well. I know on the internet there's always the danger of being spoilered accidentally and that's not what I'm taking an issue with. It's solely the people who are incapable of basic internet etiquette.
There's a place for spoilers in topics about the specific media. With massive spoiler warnings. If the topic is not specifically that piece of media but you want to make an example, mention the spoiler is for that piece of media. Or just allude to an event so people who know it will recognize what you mean but those who don't, don't.

It's not that hard.