Because, if my memory serves, that's the definition of peak oil.
Peak oil is the peak of the curve `energy extracted/energy expended to extract it`. Since 2017, this has been decreasing.
*edit* I realize that the definition of peak oil I've been using (which I believe I've found in the writings of Jancovici) is apparently not the standard definition. My bad.
I feel one thing that few bother to understand is that it would be extremely hard to arrive at "no more oil", even if humanity somehow made a good faith effort to get there. There is oil all over the place on earth. It's not necessarily oil that's economical to extract, even by today's XXX (pick your term) corporations. There is also energy all over the place (again that might not be economical or politically correct to extract right now.) The result of this is that if NNN years in the future you need oil for some worthy reason (say, you need more Legos :-), you can collect and spend the energy and get the oil. That's not an issue.
Peak oil is the peak of the curve `energy extracted/energy expended to extract it`. Since 2017, this has been decreasing.
*edit* I realize that the definition of peak oil I've been using (which I believe I've found in the writings of Jancovici) is apparently not the standard definition. My bad.