I suppose these pods are most popular among suburban dwelling, office working people whose clothing is consistently soiled.
Common sense says you will need more detergent on heavily soiled items than ones lightly dirtied. People who do physical work will have some clothing heavily soiled, and others not so. The pods would be difficult to adjust for soil levels and types.
My sister, whose husband is a farmer, uses both liquid and powder detergents. Greasy garments from them working on equipment are usually cleaned with the liquid, and items soiled with ground-in dirt from the fields are washed using powdered. Sometimes they have both, and are pre-treated with liquid, and some powder used also.