You are the one making cost an issue! Otherwise your resistance makes no sense, because retrofitting of some structures is better than no retrofitting of any. No one has said we oppose requiring it in homes, but that is not what is being debated right now. Using your logic it would have been wrong to ban cigarettes unless we banned all forms of tobacco. 
When you account for the number of people living in single family homes vs condos, are you sure more people have died? And if so isn't that because newer condos have been required to have sprinklers, therefore making the point?