Can someone explain to me why people want to cut deeper?

To start off with this post: I'm not judging anyone or anything for this, I'm asking out of pure curiosity.

I've struggled with self harm for a few years now. They were always epidermis cuts and I wasn't intending on going deeper at all. I accidentally went abit deeper and I couldn't go back to the epidermis cuts cus they didn't cause me enough pain no more. But I see people online setting goals on how deep to go and when. Why do people want to go deeper voluntarily? I find it hard to understand so if anyone could help me out it would be great :)

Also, please dont use terms like ' cat scratches ' and ' beans ' those are extremely invalidating and should not be used.