**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 

[![enter image description here][1]][1]

*[Image source][2], example, not endorsement* 

or Polaris connectors 

[![Polaris connector][3]][3]

*[Image source][4], 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.


  [1]: https://i.sstatic.net/MKU5hZpBm.jpg
  [2]: https://media.ilsco.com/image/itemimage/MAC-618-T-K.jpg
  [3]: https://i.sstatic.net/A2Bx9pO8m.jpg
  [4]: https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Fimages.thdstatic.com%2FproductImages%2F7040118b-679b-4964-b468-b95653c26ada%2Fsvn%2Fpolaris-wire-connectors-wire-terminals-it-3-0b-64_1000.jpg&f=1&nofb=1&ipt=98728f152a6fe22c136556c2633db0eac4c9e72892828c8759007843b7e606f4&ipo=images