Large corporations are allergic to capital expenditures. That is, they don’t like investing in new things to make the business run. They want their previous investment to run as long as possible. On occasion, the workers will arrange things to be covered as “maintenance” rather than capital expenditures.

Oil companies have invested in oil pumps and refineries. They could invest in all sorts of other things, but that’s less money in the hands of shareholders. That’s all there is to it. Money spent on new investments isn’t making them richer right now.