This is debt from people who can't easily pay so the hospitals/insurance find it cheaper to sell that bundled debt to collectors. The collectors now own the debt and can put in all the work to get those people to pay. If CT buys this debt, cheap because blood from a stone, they can just forgive it instead of trying to collect interest for years

It's completely different for the simple reason that college can be a optional cost, but medical debt is often not optional. Plus these are loans already taken out being purchased at a substantial discount.