This is because kratom is an opioid. An atypical partial agonist but an opioid none the less. So it can be used for pain, sure. And as a replacement for pharmaceutical or street opioids in the same way wine can replace vodka.

It has profound dependence and addiction potential. Just take a look at the r/quittingkratom subreddit. Over 45000 members.

Caveat emptor. Seriously. It has the potential for terrible withdrawals.