Why do feral pigs breed like rabbits and javelina so scarcely?
They are different species.
Wild hogs really don't breed like rabbits. Some fish and game biologists make wild claims about wild hog breeding habits. They take statistics from domestic hog operations and apply them to hogs in the wild.
i'm not a fish and game biologist: i have spent untold thousands of hours hunting, trapping and simply observing wild hogs. Wild hogs very seldom have more than one litter per year.
After shooting and trapping many hundreds of wild hogs, i can say that wild sows seldom breed before one year old. Most of the one year old sows i trap have never had a litter and are not pregnant. It's quite common in SW OK to kill sows 2-3 years old that never had pigs. The average litter size is 4-7 pigs. Seldom are more than seven pigs encountered while field dressing pregnant sows. In a year when theres a bumper crop of pecans and acorns the sows get fat and have large spring litters.
If a wild sow raises half her pigs to 20 pounds shes a fine mother. The coyotes and bobcats get some pigs. Heck: 10-15 percent of domestic pigs die.
A wild hog has a hard scrabble time finding enough to eat. The javelina in a desert environment have a harder time.