who's your daddy?

One of the reasons that the rocky planets in solar systems with more O than C are made of silicates is that mainly O and Si are left after most of the carbon pairs up with oxygen to form CO₂.

Note that even trees on earth (not to mention animals) are made of carbon temporarily pulled from the gas phase onto a planetary surface. 

This is how our atmosphere, thankfully, reacts with the planet and sunlight to form a living crust.

We get water and nutrients from mother earth, but the ground state for the carbon of which we're made is CO₂. It's a key part of where we came from, and it carries away the carbon weight that we (and organisms which prey on us) metabolize. 

Civilization may produce many gases harmful to the environment that are mere pollutants.  Carbon dioxide is not only that.