Thats the point you miss- because NPCs are so weak it allows solo and PG to be the most efficient route to do anything.
They do have strong NPC - but they choose not to use them
Why?
Maybe because the vast majority of players are flying crap ships that are in real danger from the current types of NPCs? Could be.
I'd argue to that Powerplay was designed for PvP Open first, given that you have explicit pledges, defined territory, real time feedback, and 1:1 effort (in that, one player can make all the difference but also can lose the cycle, and be stopped directly if it all lines up)
Everything you mention works as good if not better in PG or even in Solo.
If Open gets deleted from the game tomorrow, BGS and PP will work as good if not better - simply because people will focus on activities that matter for BGS/PP and not roam the system in G5 murderboats trying to get a kill.