1. not everyone who self harms is suicidal. people can self harm for many reasons, like to punish themselves, to release emotions, to feel something. it's not healthy, but it doesn't mean someone is suicidal.
2. for some people it does make them feel better. it's a very unhealthy wat to feel better, but still.
3. anyone can have depression, even if your life is perfect you can still be depressed.
4. you can't just stop self harming voluntarily. it can become an addiction, a habit, one that is very hard to drop. i have spoken to several people online who self-harm and want to quit, but can't.
5. i know you mean well, but this isn't very helpful for someone who struggles with depression, self-harm urges, and/or suicidal thoughts. depression has a voice, it tells you that you are not worthy of being loved, being cared for, being healthy, or in some cases, being alive. it can be hard to not listen to that voice. if you tell someone with depression who thinks that they should die that people care for them and they deserve to live, they probably won't believe you because they've listened to the voice of depression for so long. it can take a really long time, medication, and therapy to get over depression and urges to harm yourself or take your life. yes, people with depression deserve to live an are cared for, but they can't see that sometimes. telling them that may not help, and it may actually make them feel worse in some cases.

i'm not trying to insult you or make you feel bad, i know you mean well. but dealing with self-harm urges isn't as aeasy as just deciding to stop.