Because that's still geological carbon entering the overall cycle on the surface. The air and ocean are giant buffers of it. When it's needed it needs to be pulled from there somehow (such as by felling trees or directly extracting CO2). Unfortunately that's not economical when it's legal to tap the giant lakes of it sitting underground.
Many of the other things (plastics esp) are byproducts after refining for fuel. If the fuel isn't consumed, the byproducts would become cost ineffective.
Don't "worry" though. Oil consumption is going up not down.
I understand the not burning fossil fuel thing, but why can't it be seen like another mineral resource?