Selection bias. You found the lucky plants that managed to live. I had a friend try to grow shrooms, and despite managing the humidity, temperature and light exposure, disinfecting the container, and carefully controlling just about every aspect of the process he couldn't get shit to grow.
Likewise when I was strapped for cash in college I briefly considered growing a few cannabis plants and decided against it after it seemed to be a lot harder to grow anything sell-able than expected.
I've always considered the main reason we don't have a larger home grown drug problem is the same reason high-end crime is relatively rare: you're selecting a technically capable subset that our society already rewards fairly well.
Such is the setup of Breaking Bad: were Walter White not terminal, would he still take the risk?
That and the fact that police techniques for locating this kind of thing is pretty advanced. Until recently (LED grow lamps) the power consumption from grow lamps was so high that the power company would notice and the police would take interest. Cops can also drive around with infrared cameras looking for hot exhaust air/lamps, visible even if windows are blocked. Helicopters with infrared cameras can see hidden grow plots outside.
Even when I was looking at it people were still split over LED vs conventional lights for growing, so it's only gotten easier to evade detection as the legality of growing has relaxed (literal definition: become less strict again).
I don't know about shrooms, but they're peanuts compared to weed anyway. Obviously it's infeasible to grow coca anywhere in the US- you need a huge amount to produce any drug. Likewise creating LSD/MDMA/meth without synthetic, highly controlled precursors is pretty much completely infeasible. You could grow morning glories for ergot... if you wanted to harvest an entire field of them.
But yeah, any decent chemist could figure out how to make any of the big drugs very easily. The precursor restrictions only keep out the non-experts. Even a penniless chemist knows that going to jail for that will make him totally radioactive for the rest of his life.
That's not a counter, it's more selection bias. Nature is a good place for mushrooms to grow, but that doesn't mean it's easy to grow them yourself. Cannabis is a very successful plant but it still isn't as easy to grow in your home. You can go outside and find a fern almost anywhere in the world- they're one of the oldest, most successful, and most widespread plants, but they are a pain in the ass to grow yourself: http://articles.latimes.com/1991-10-27/realestate/re-649_1_m...
Sorry, I may have been too vague. I grew them in a large plastic bin in my bathtub. I got the spores and was able to start the mycelium without any bacteria problems, somehow (My kitchen was no more sanitary than you would expect from a 21 year old bachelor). I really had no idea what I was doing so, based on the stories I hear of other people trying and failing several times before giving up, I assume I was just exceptionally lucky. :)
Edit: Ah, I get your point about selection bias now. Yes, based on self-reporting on drug forums I am surely in a small minority of clueless yet successful psychedelic mushroom farmers. I suppose if I ran through a minefield once and didn't lose any limbs, I would think that was easy too: "just run in a straight line as fast as you can, no problem!"
I also had success growing mushrooms at around that age.
I just followed the instructions and did try to take extra care with cleanliness, my guess is that as we're both here on HN we're probably predisposed to be better at following a process.
Likewise when I was strapped for cash in college I briefly considered growing a few cannabis plants and decided against it after it seemed to be a lot harder to grow anything sell-able than expected.