Why does store-bought peanut butter in a jar have so much more oil than fresh ground?
Having recently made peanut butter by hand,
(Using an hand cranked food processor).

I can say after looking at the result, over the last few weeks.
My peanut butter is much more oily than store bought.
It has also separated more.

The only trick to making your own peanut butter is the process it more than you thought.
When you think you are done, keep going.
I thought it was done when it was a kinda smoothish but crumbly texture.
But I thought i would give it a extra half and hour (Hand cranked remember).
Then it really became the oily smooth peanut-butter we know and love.

Peanuts are incredibly oily.
But exactly how oily is going to depend on several factors.
Things like growing conditions (Tempurature, soil etc),
and things in preparation -- how much (if at all) were they roasted (at what tempurature), how fine was the grind, what excess oil separated off.

Commerial peanut butter can control these things by sourcing peanuts from same set of farms (or by just combining such a huge number that you have the average peanut of a nation), and by using consistent processing.