Earlier quoted context omitted.
You mean like supplements, which exist today?
Experimental drugs cannot be given freely like supplements.
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?