Just because something, when used a certain way, has positive benefit doesn't mean it should just be sold to anyone that wants some.
I bought a pack after I had surgery- I never finished it and never expect to take it again. In a large way it feels gross and unpleasant, completely unlike codeine/vicodin/oxycodone. (I don't feel like I ever got addicted, despite taking it daily for a couple weeks, and haven't taken any opioids in the 8 months since the pain stopped interfering with my life)
Sure, people can also go on a DNM and with bitcoin they bought with a credit card order as much cocaine or heroin to their door as they want but most people see cocaine and heroin as bad and would never do that.
However, when you have people on podcasts and YouTube going on and on about how great kratom is, how kratom makes their anxiety better, how kratom helped their friend's cousin's room mate's girlfriend get off heroin, then people are like "oh shit, I'm gonna order this panacea" and you have people that likely would never have tried some random opioid ordering the substance and consuming it.
People will try something if it becomes part of a (their) culture or when someone they put trust in talks well of it (podcast host, YouTuber they follow). Look at when people discovered hacking productivity with Modafinil, you had domestic and foreign websites popping up like crazy selling real modafinil, fake modafinil, super harsh on the liver pro-drug versions of modafinil, to anyone that had a credit card all because a few tech journalists reported on how some in silicon valley were using it to hack their productivity.
Look at 'k2' and similar synthetic cannabinoids that popped up several years ago. People were all 'hey man, it's legal and like weed!' and within months it was for sale in every headshop and even many independently owned gas stations. And whoops, once you had a bunch of people trying it turns out it wasn't exactly like weed and people were having basically bad trips and even seizures from mild to moderate comsumption and then state after state quickly started making it illegal.
Then 'bath salts'.
Go back 20ish years and kids were fucking around with freon and dying because it quickly entered certain cultures as a free way to get high at home.
We live in a world where ideas are highly contagious. While kratom does seem to have benefit in some cases when used correctly and does have a traditional use, it just shouldn't be something that John Q Public can hop on the clearnet and order for self-medicating.
I see regulating kratom as just a chance for healthcare and pharma to take a cut of a substance that's in demand, by controlling the market for it.
Step 1: see substance in high demand because it actually has physiological effects.
Step 2: identify potential harms.
Step 3: claim that because of these potential harms, only highly credentialed people are allowed to administer the substance.
Step 4: profit.
The hypocrisy with regard to alcohol and common household chemicals should immediately dispel any arguments about harm reduction being the driving factor in drug regulation. Not to mention substances that have publicly been identified as harmless (or at least, within the ability of every day citizens to self-administer) in the scientific literature, but are still regulated because of concerns that deregulating them will "set a precedent" and "trigger demand for more deregulation." (https://www.ncbi.nlm.nih.gov/pubmed/9524840)