Because they don't care! Really most people don't know you so they don't care about you. If there is a burning building, are most people going to rescue themselves or sacrifice them self to save other people who they don't know? They are going to save themself. If someone says, "They are insecure about themself," they are stupid. If you're insecure about yourself then you are not going to make fun of people to make yourself feel better (Unless you have a mental disorder or are stupid)
If someone makes fun of you on the internet, they are prprobablyomething call a troll. Trolls are people who get pleasure in saying random, weird, gross, mean ect. stuff to random people to see their reaction. If you want people to stop being mean, don't get offended by it. If you don't react, they don't feed off of it.
I hope you understand and I am breaking this down well enough for you, Sincerly, M
most people are suprisingly immature,even people you'd think are really together.think about the way a child acts; selfish, no class,don't think about how they're seen by others ect... most of the ways children act we assume will be grown out of,sadly it seems most people don't really make much emotional progress past age eight or so. they learn better ways of hiding it as they grow,but end up giving themselves away anyway. can't hide our real natures very long. it is a drag though isn't it?