Because they were originally aired at that time of day when mostly houseviwes were home, so the commercials were mostly about detergents and household appliances.
Because in the States in the 60's television drama was sponsored by soap powder manufacturers, ie ' this drama is brought to you by Proctor and Gamble , makers of super white washing powder. Ad...
Early soap operas were usually sponsored by soap companies (on up to present sponsors such as Procter & Gamble) as a good way to appeal to their housewife customers. Calling them "operas" is...