Why do we remember people when they die, but never when they're alive?

That is not true.

Don't we tho?.. but you only die once.. you keep living for days

It’s the finality of death

Because you do not know what you are missing until it is Gone, right?

You’re all strange. I think about my family all the time.

Because of life. You have your own bills, problems etc.. you are not going to be thinking about me because you are focusing on what you have going on in your world. But people often think of others even though they may be busy, the other person just doesn't know it.

Human nature

No one cares unless one is beautiful. Rich or dead.

That’s a generalization that doesn’t apply to everyone.