it's all about profits. the bung-holes who build apartment buildings want to spend as little money as possible, to build as many apartments as they can. they will build toward a target demographic, and will not spend one cent more than is required to attract that market. the extra construction money/time that would be required to construct solid buildings with some insulation and sound-proofing is not a required expense. the bung-holes aren't going to live there, after all. they care little about the misery of the apartment dwellers - people whom they assume to be a transient population, anyways. the bung holes just want the complex to look appealing enough to get folks in there a year or two, then repeat, repeat repeat.