Most, if not all, people who have tried cannabis, and even gone onto become true aficionados, would likely agree that the first encounter with cannabis is quite anticlimactic. In fact, many people don’t get high until their second, third, or even fourth and fifth time consuming the herb.
This remains largely a mystery that hasn’t been explored by legitimate scientific studies, probably because of its lack of groundbreaking implications. With that being said, like all unresolved mysteries, it always sparks curiosity, especially of all the cannabis enthusiasts who have pondered over it for years, wondering where they went wrong that “special” first time.
Here are a few theories for the disappointing first time(s) consuming cannabis.
Underdeveloped Cannabinoid Receptors
THC is believed to actually stimulate the production of cannabinoid receptors. If your body has never received THC, then your cannabinoid receptors are likely underdeveloped.
Some people believe there’s a glaring hole in this theory – some people do get high their first time. However, while these are all speculations, what is certain is that the glaring hole is actually in this particular theory.
Firstly, CB1 receptors can come in different variations and mutations, which is why the effects of cannabis can be quite individualized altogether. 
Another factor to consider is something seemingly irrelevant – working out. It’s a widely-known fact that voluntary exercise, especially during adolescence, stimulates the production and sensitivity of CB1 receptors and generates endocannabinoids, which are credited for the famous “runner’s high.” 
So, people who work out basically work their brains’ CB1 receptors out as well, preparing them for the real deal, and when the time comes, their brain can rise to the challenge.
As you may know from experience, nothing snaps you out of that sweet daze like sudden fear and getting startled, and those experiences are always accompanied by heavy hits of adrenaline.
Again, this is just a speculation, but it is possible that the adrenaline, pulsing through your body before your long-awaited first time, might actually dampen the effects of cannabis. The next time(s), you’re naturally more relaxed, possibly even skeptical, which ironically opens your brain up for cannabis to work.
Finally, it’s also possible that you based your expectations on movies and music that depict being high to unrealistic (or not) extents. When the first time paled in comparison because of the aforementioned reasons, maybe you just dismissed the experience altogether.
Again, these are all speculations, but underdeveloped cannabinoid receptors seems like the most plausible, and more importantly physiological cause, which could also explain why this phenomenon occurs on such a large scale.
- Smith, D. et al, “Rare genetic variants in the endocannabinoid system genes CNR1 and DAGLA are associated with neurological phenotypes in humans”, PLoS One. 2017; 12(11): e0187926. Journal Impact Factor = 2.766; Times Cited = 10
- De Chiara, V. et al, “Voluntary Exercise and Sucrose Consumption Enhance Cannabinoid CB1 Receptor Sensitivity in the Striatum“, Neuropsychopharmacology. 2010 Jan; 35(2): 374–387. Journal Impact Factor = 6.399; Times Cited = 76