E. B. White's Charlotte's Web certainly does bring up the issue of raising runt pigs. When raising pigs for food or to sell as food for profit, size matters. Runts, even when fully grown, will never reach the size of their peers. Pig market experts warn that sellers often try to "pass a runt on from litter to litter" and that an "alien-looking piglet may be a year-old midget" ("What to Know Before Buying a Pig," p. 3).
The weight at which it is considered acceptable to take a pig to the butcher is between 225 to 300 pounds; we call this the market weight ("How Much Meat From a Pig"; "The Cost of Things--Pigs"). A pig will weigh about 225 pounds at the age of 7 months old; a farmer wants to only butcher a young pig because "the meat is at its most tender" ("The Cost of Things--Pigs"). Also, the longer a farmer raises a pig, the more expensive it becomes to raise the pig, so the farmer will lose profits. The market weight is decided based on what it costs to butcher a pig and how much meat the pig will yeild. Based on today's rates, it costs a total of $535 to both raise and butcher a pig; a butchered pig weighing 250 pounds alive will yield 150 pounds of meat fit for retail, which will fetch a retail price of $3.56 per pound ("The Cost of Things--Pigs"). Therefore, any pig weighing less than 250 pounds will not yeild any profits for a farmer.
It's also important to know that runts are a bit different from just "undersized pigs" in a litter. Undersized pigs, when given the nutrients needed, will eventually catch up with their larger peers. Runts, on the other hand, have actual physical defects, "do not grow well and many die within a few weeks of birth" (Alaska Livestock Series, "Recommended Practices for Raising Pigs from Birth to Weaning"). Runts who do survive when raised on bottles are usually illness ridden.
Hence, it's simply neither profitable for a farmer nor healthful for the pig for a farmer to raise a runt.