Placing a plastic pipe over a junction box does not provide the protection offered by a 50-cent cover plate. I don't think a responsible electrician would have left the boxes uncovered.

He explained that plastic junction boxes are more common in residential settings. Because plastic is a non-conductive material, models made of the material cannot be grounded.

A suitably-sized plastic junction box is a good starting point, but it takes more than that to make a functional enclosure.

NEC requirements for covers for pull boxes, junction boxes and conduit bodies ...

Anytime you have an electrical connection made, it needs to be housed in an accessible box, as per code. For example, if the fixture over the dining room table is 12 to 18 inches off center because of ...