Neurotypical people don't do any form of self-harm typically, even punching walls. It's unnerving to see people causing themselves pain due to empathy at seeing someone in pain and because it simply doesn't form part of their psyche to think to do something like that to themselves. The vast majority of people value their own lives and are protective of their bodies even if they have issues with themselves at times. It's also seen as a waste and a statement that you don't value yourself and possibly by extension life, which will usually provoke ire. It can also be seen as attention-seeking which people don't tend to have much time for. This applies to most things in life but deviation from societal norms has the effect of people mistrusting or shunning you and feeling uneasy in your presence, at least with strangers, but most will feel a little sorry for those who self-harm again due to empathy. If I imagined someone I cared about and they had scars or cuts from self-harm I'd be upset because it's sad they can't see their own worth, there's no need for them to do that and it's a shame. They are attacking themselves because they are hurt, you just want to take the hurt away from them and tell them how much they mean to you.
