Mother nature’s design is such that she always prepare her children for future. As far as top layer of soil is concerned, she planned weeds and grass.
This live mulching continuously transform Father Sun’s radiation into biomass. Natural inverters in your urban slang. This biomass is very critical for future nutrition for the soil, plants and other local habitat.
So when we use brain-dead practices like applying herbicides, we not only disturb nature’s cycle but also lose essential bio-mass.
Btw, what we call गौचर or grazing land, has highest efficiency to transform sun energy into bio-mass. (wheat 0.2%, rice 0.3% and grass 4%) So wherever grass lands are fit in the setup, they are blessings, not only for cows but also for soil. Her fertility is protected.
So when grass grows, it is not useless. It is supplementary biomass requirement for less-efficient wheat or rice or corn and soil where less-efficient crops are planted. She anyhow have to protect her fertility, in the larger interest of the ecosystem.
Think about it (Y). Experiment. Educate.