pipes
The job was done correctly, the right parts were used and there was simply no need to glue the bottom end of the vertical pipe going into the hub below ... and now a repair will be easy if anybody ever breaks the plastic
Using that logic, there would never be any reason to glue the top joints of ANY fittings because the water would never create any pressure on them. In this area, YOUR joint WOULD have to have been in place during the water pressure test, and it WOULD have leaked and WOULD have been rejected. Anyone who uses a plastic flange is setting themselves up for a future repair, but that is not justification for making an improper connection, and if it was not cemented it was NOT done correctly, and it was a handyman job.