Why is $RuBisCo$ enzyme the most abundant enzyme in the world?

(N/A) $RuBisCo$ (Ribulose$-1,5-$bisphosphate carboxylase-oxygenase) is the most abundant enzyme in the world because it plays a critical role in the primary step of carbon fixation during the Calvin cycle in all photosynthetic plants.
It is estimated that $RuBisCo$ accounts for approximately $20-25\%$ of the total soluble protein content in the leaves of plants.
Since photosynthesis is the fundamental process for biomass production in almost all ecosystems,and $RuBisCo$ is essential for this process,it is present in massive quantities across the globe.
It is often cited that for every $1000 \text{ kg}$ of protein produced on Earth,a significant portion is represented by this enzyme.