Drugs are reliable, in that their effect has no bearing on the mood they are in, as chemicals don't have moods- unlike friends. Chemicals don't hold grudges, they don't hate. They also don't remember or love either- despite some producing feelings so profound one could describe it as pure love in concentrate.
This is, however, only half of the equation. The euphoria is inevitably followed by dysphoria. Manic pleasure followed by anhedonia. Endless epiphanies followed by endless despair. And I say endless in a metaphorical sense, as all things have an end, although in the moment it may not seem so.
Forgoing the legitimate uses, generally drugs appear to be a great solution to an immediate and urgent problem. Truth is, the solution is a short-sighted one, and one that leads to more and more problems and fewer and fewer solutions in general.
The thing about people, specifically trusted family and friends, is that they will let you down, just as you'll let them down. Part of it is due to the flaw in our expectations, the other part is due to the fact we are imperfect creatures, and perfection is an admirable goal although an impossible one. The bright side is, that these failures and short-comings can be addressed, corrected, and repaired- then ultimately leading to a better future. Much different than the future that the drugs will take you down- even if they never 'let you down'.