Different strains, and even different generations of same strains all have different thresholds of stress that they can deal with. It is a self preservation response from the plant itself, whose only known purpose in life is to reproduce, not grow huge buds, multiple colas, or sticky trichomes. I’m sure that it’s beyond time and space consuming for breeders to stress test every single strain they release multiple times before they release a stable one. Especially when the market is driven by popular strains and high thc levels. A breeder who is trying to stay current with trends isn’t going to make it to market if they have to make a cross, bring it to maturity, grow its offspring, and then hunt for that perfect phenotype, and then grow multiple generations of that phenotype until they have a completely stable variety. Then factor in the popularity of feminized seeds vs regular the highest ratio of female to male in feminized seeds is like 90/10 . I’m not a breeder on purpose, only once accidentally. But I’ve watched enough documentaries and read enough to understand what’s involved in creating a new strain of weed. But more importantly I stayed at a holiday inn express once so I know stuff