Because they are inexpensive. Manufacturers know that most users do not take the time to become aware of the dangers of these products. We have discovered a way to blend several substances in a way which produces the same effective cleaning power as the hazardous cleaners, at a cost comparable to hazardous cleaners. Emulsifiers break dirt and grease into small particles. Coupling agents allow grease and water molecules to combine so they can easily be washed away with plain water.
Detergents keep dirt and grease particles suspended in solution so they are completely removed.
New dirt will not form so quickly. This allows a longer time between cleaning jobs. Each time a bubble breaks it scrubs off a little more grease and dirt. Specialized builders clean dirt from hard surfaces, reducing need for scrubbing. They also condition the water, eliminating need for water softeners.