PowerPlay is (apparently) meant to be a credit and time sink. That's the only reason it takes longer to pick up 25 merits (at rating 4 or 5) than it does to pick up 792 tons from the market place. It's the only reason it takes longer to drop off 25 merits than it does to drop off 792 tons in the market place.
The amount of stuff that needs to be improved in PowerPlay is borderline ridiculous - from UI and UX to massive bugs that actively breaks the rules of PowerPlay, but since its inception it's apparently been hamstrung by internal office politics. Clearly someone in charge is personally offended by it and has been doing their utmost to keep any kind of attention from being given to it, and as time went by they became more and more effective at it.