There is some merit of intentionally not PP maxing your moves that I have seen be relevant in VGC:
- Encore will end early if a Pokemon runs out of PP on its move. For moves like Gravity or Trick Room that can often be bad to be locked into, not maxing PP can help you break out of Encore locks in certain lategame scenarios. Some players opt not to PP max Detect/Protect for similar reasons on cartridge. I would have won a game at North American Internationals this year if my Xerneas only had 10 Protect PP rather than 16, because I was got in an Encore lock vs Whimsicott but my opponent also couldn't do much damage to it, and I managed to get enough double Protects that I would have done 10 in a row.
- Choice locked Pokemon with moves that only have 5 PP sometimes intentionally opted not to PP max so they could Struggle sooner to be able to hit Shedinja. The most common example of this was Choice Scarf Kyogre with Water Spout; you often couldn't afford to drop another moveslot for a move that would hit Shedinja, so the next best thing was to speed up the process of getting to Struggle.