When signals wander between channels of different cables, line capacity takes a dive. Near end specifies that the interference derives from an adjacent pair of cables at the same location. Signal intensities fade as they traverse copper cable, especially signals at high bit rates and higher frequencies. DSL is capable of. Lower-resistance wire can minimize attenuation, but any given service provider may not deem the expense justifiable.
Thick wires have less resistance than thin wires, but they also carry a higher price tag.
Due to reduced attenuation, 24-gauge copper cable permits conduction over greater distances. When the PSTN was populated only by voice calls, load coils squeezed more distance out of phone lines-a wholly commendable pursuit. Prospective DSL subscribers cannot get DSL service until load coils no longer reside on a copper run. When the phone company doesn't feel like totally disconnecting an unused section of cabling, it takes a shortcut by installing a bridged tap. These practices never seemed to bother anyone until the rabid demand for DSL emerged.