why do people think that if a person is truly going through something they won't ever speak up about it?

recently i saw a video that criticized people for talking bad about themselves and saying that life is cruel, their life is shit and things like that. the people in the comments are saying if a person is truly going through something and has mental health issues they would stay silent and not let everyone know that they are suffering. i personally strongly disagree with them, but I'm curious to know y'all's opinions and the reason why do people think that if a person speaks about their problems they don't actually have them and are just asking for attention and their problems are invalid.