This assumes we use the oil purely due to its energy content. Which is true in some sense or the other, but unless you can replace all uses of oil derivatives with either synthetic sources (that don't cost significantly more energy to create than the oil extraction would) or something different altogether (e.g. in the "producing electricity" use case).

And even then, who knows whether dumping spare electricity into oil wells instead of e.g. batteries or pumped storage hydroelectricity might remain profitable.

My point is, it's not necessarily that obvious, and we better not wait for people to stop running out of ideas to make a profit on fossil fuels.