Who`s guilty?-Architects or Constructors?..?

All those who live in multy unit buildings know how there is no sound proofing between the floors and adjacent apartment units, as one complainant said, 'whole day & night long she has to listen to her neighbors in next townhouse'.With no sound proofing in between units, you have to listen to, and smell your next door/floor neighbors-24 hours a day.I have lived in several countries and know for fact, that this kind of cheap construction-with hollow floors/walls-is typical only for U.S.-no where else.One expert on line claims that it is the way architects design buildings in U.S., but I think architects design according to builders orders, and it is the builders, who want least expense & most profit who are to blame for these chintzy, poor sound proofing buildings so typical for U.S...So who is to be blamed for this?..architects or constructors?