People selling stuff are in the same category as the drug companies; I have no objection to regulating them, and imprisoning them for fraud, with an enhanced penalty for preying on particularly vulnerable people in the case you described.
Of course they can. You take any molecule, put it in a pill bottle, disclose there's no clinical evidence of its efficacy and you can put it on store shelves. There are thousands of such products on the market today. Stores will often put these in a section called "Supplements" so that people don't mistake them for medications which have proven their efficacy.
These molecules generally don't do anything of substantial value because it's incredibly difficult and expensive to produce a molecule that does anything of value. If you're going to undertake that billion dollar effort, then you're going to want consumers to trust it, pharmacies to carry it (near the medications, not the unproven supplements), and most critically: insurers to pay for it.
You do not have to seek FDA clearance to sell your molecule to consumers. To achieve marketing objectives necessary to recoup the development costs of a working molecule, you choose to seek FDA clearance.
What exactly do you think distinguishes an "experimental drug" that's not going to be put through trials from the thousands of other unproven molecules typically sold on aisles labeled "Supplements" or behind the counter at gas stations? Your hope, belief, or presumption that it actually works?
If the manufacturer creates the substance with the intention of treating a disease, then the substance falls under FDA restrictions, irrespective of whether they make explicit claims about its medical benefits.
