If it's aluminum, cost savings while doing the job would be the reason - most electrical distribution is aluminum conductors for that reason.
Depending on wire size Mac-Block
Image source, example, not endorsement
or Polaris connectors
Image source, example, not endorsement
are approved methods of joining aluminum and copper wires. Use a torque driver and tighten the screws on the connector to the manufacturer's specification for the specific connector and size of wire, neither too tight nor too loose.