Its all about the numbers guys. Stature chart.
95% of boys at the age of 20 years old are under 6 ft. 2 inches (74 inches). So, assuming that we don't grow any taller after 20 years old, which I believe is true, the height number holds up for adult males as well (though the weight numbers certainly do not).
Assuming that those 6 ft 3 to 6 ft 5 can wear a 36 inch length pants, that may be only about 2% of the population (since there are likely equal numbers at the bottom of the chart) . Then you take that 2% remaining and try to determine how many of those have 34 inch waist. With our overweight population I am sure that you can say that at least 1/2 of those are above a 34 inch waist. And on top of that there must be a number of teens and others that have less than a 34 inch waist. You are then left with about 0.5% of the male population at my guess, and that might be generous.
So if you are a retailer and have limited shelf space or $$ for online inventory, what would you do? I am just thankful for those that even offer 34x36 and I hope that our collective online numbers can be a market that will justify some focus and expanded options.