Because we have to trust people some times. Bitcoin doesn't scale without a little bit a trust. Every individual gets to decide how many sats they use here and where they move them. I believe in stacker news and the people behind it. I will trust a little bit of my sats to sit here so I can exchange them more easily. This is how Bitcoin scales. If it isn't good enough, don't use it. When you pull out the credits you get Bitcoin. If you don't trust stacker, don't use it.