Agricultural practices depends on Tradition, Availability of land for farming,budget/capital, availability of labor, water and attitude of the farmer. 
In a rich family, we often see one child policy and devotion of full time and resources to him/her. While a poor family often have many children with parents
negligence towards there education, insurance, investments, etc.
While being in a corporate farm, I found the Chief to be very selective in crop selection, spacing, fertigation, weed removal, etc. They had enough land, labor, capital and other resources. I had the opinion that dependence on one crop is risky and focus should be on land resource utilization. In this the inter-crops should be allowed or else the weed removed should be sold as a feed or composted or used in some other farming activity. But when a crop has good market demand, the farmer's focused attention is on that crop and he/she will not like to divert the resource and attention to other crops.
Market driven farming is one thing while farming for personal need, seed, nursery, research, hobby, environmental concerns, etc. is another thing. In a given agro-climatic location a plants survival and production status can be very well, but if the market demand is not favoring the crop, than it becomes a weed. A farmer's attitude and "whims and fancy" has also huge impact on considering a plant to be a crop or a weed.
Food processing and mixed farming can make a weed or a crop with a high production but poor market demand, to get converted into a product with high market demand. In this the conversion into alcohol is often tried, but some Governments ban on alcohol, hampers such processing. Conversion of a crop into energy rich fuel, medicine or other items with high shelf life is often followed.
Communication and marketing evaluates and creates demands. Packing,Transport and financial liquidity in transaction, helps to meet the customers requirement. Mixed farming with crops, cattle, Apiculture, Mushroom, other economically important animals like, poultry, fish, dog, etc. helps the farmer to realize in capturing different markets and meet his/her nutritional and security requirements.
