When I see traps like that I tend to blame the roofer ..... last year I caught one in the act of removing the trap from a rtu drain as he was also on site because of a water leak. Said "I'm just helping you out because someone installed the drain wrong"
I used to PM McDonald's cooking & refrigeration equipment. As a favor to them, I'd also remove & flush their RTU traps because they'd often grow a blockage.
I never understood why their maintenance guys saw some reason to go and plumb all their three or four RTU condensate drains together, then run it all through a common PVC pipe to the edge of their flat roof.
Are they afraid to get their roof wet?
I often see that too where they go through a lot of trouble and pvc material of piping an elaborate draining system on the roof to expel the water into a rain drain or close to it. I often scratch my head of what's the point?