Because it is relatively evenly distributed so it has no effect on the weather. OTOH the distribution of water vapor measured by satellite is a critical input to weather models.
However, satellite depictions of CO2 are available, like this one from 2009:
It shows that CO2 is modulated by weather. There is less in colder regions. There is a bit less east of the Amazon rainforest. But there is more in some parts of the NH where the weather patterns allow it to stack up. But unlike water vapor, these are all relatively small variations.