Just a thought I had, The average penis is 5,75 x 4,75 why there are fewer bigger than 6.5 or something and beyond that the percentage is lower. A poorly nourished body means a poorly developed penis too ?
Let's bring in the full picture across the millenia. This is based on data, and not speculation.
You have three groups of male's genitalia, and of course, the three group can be broken down further into smaller subgroups. But, we'll focus on mainly three. The first group is the below average, which is anything less than 5in x 4in. Based on the 2018 tallied data, and guestimated for the worldwide population, it's around 39.5%. The average, is anything between 5in x 4in to ~5.5in x ~4.5in. This makes up around 56% of the male's population. I was in this zone for a very long time. Anything larger, well, those are blessed. This is the ~4%. The subgroup to the above average going past 7in x 5.5in, those are considered monstrous. This falls within the ~0.4%. Anything past 8in x 6in, these are no longer normal human but a class of their own. You're talking about less than 0.1% of the male's population worldwide.
The data had only been collected from "surveys", and you know how reliable surveys are. But with the tallied data throughout the millenia worth, modern data have extrapolated sufficient amount estimated length for the male's averages. Female's expectation of longer, larger, and more pussy-stuffing sizing beyond the averages, well, they probably hung around areas where males with blessed sizes did and still are doing their pussy hunts.
As for poorly nourished body, it does not equate to poor penis size. Those with genetic disposition can have very long and skinny penises, short and very thick penises, and everything in between. This only occurs during physiological developmental phases. Genetics happen to play quite a huge role in limiting the penis growth, unlike breasts. Breasts have both influences of genetics and dietary since fat is needed to influence larger developmental sizes.
However, there is a factor that causes the penis, and breasts, to increase in size even if there is a hard limit on the penile growth. The flooding of hormones during developmental phases can shift the growth limit. This has been proven over and over gain both in males and in females. Unfortunately for us males, there are more hormones influencing female developments over males, causing us males to have a downward developmental shift. So, in about 20 to 30 more years, the average may shift very significantly to smaller sizes.