D&D PC's have never been some guy just off the farm.
In YOUR campaigns. Others obviously have different experiences.
D&D PC's are based heavily in Pulps and pulp heroes are not just some guy off the farm.
Many pulp heroes started off as regular joes- possibly with a small advantage here or there- who fell into extraordinary circumstances.
Buck Rodgers was a gas inspector who was overcome in a coal mine and woke up hundreds of years later. Nothing in his origins shows him as being destined for greatness.
Flash Gordon went to Yale and played polo. Unusual, but not superhuman. And whether he was a son of privilege or a scholarship student is unanswered.
Conan was the son of a blacksmith in a barbarian tribe and a warrior by age 15...which is not unusual. In the past, Maasai would start doing solo lion hunts in their teens to prove their manhood (due to falling lion populations, solo hunts are now discouraged).
The original Phantom- as in, the one who initially swore the Oath of The Skull- was a cabin boy on a ship. Subsequent Phantoms were no more extraordinary in origin- all very athletic, but not superhuman...just well trained.
Batman and Tarzan were orphans who were driven to succeed.
Batman and Zorro used their wealth to gain the advantages of special training. Being rich is no super power; it is not a guarantee of greatness. All that set them apart was their ethical drive to help others. To right wrongs. They could just as easily have been hedonistic wastrels.
Most pulp heroes, however, have their origins shrouded in mystery; we only know them through their exploits as establish characters. IOW, we have no idea whether they were average joes or hidden demigods.
The Shadow, Kent Allard (alias "Lamont Cranston" was a fighter pilot turned vigilante. What he was before being a fighter pilot, we don't know.
Solomon Kane's origins are, AFAIK, never revealed.