Havent seen the need for me to pledge to a power. I could see some extra payout for bounty hunting but it comes with drawbacks not worth the few more credits.
I like the discounts from the powers, for that reason i would help em out now and then but i fail to see the meaning of powerplay.
From what i see i can expand the influence of my choosen power with different game mechanics. If i spent a lot time helping my power i might get some credits every week and later some special equipment for my ship.
Credits will become meaningless later and if you gotten the special module you wanted, i see no real reason why someone should stay in powerplay.
If FD add something special for owning a specific amount of systems, then it might get some sence to do it but now ? I mean if your power owns 150 systems, they can build some battle cruisers and start wars in systems by attacking em. This would lead to more events and fun stuff seeing a power overtakes a system or other players/ powers try to defend the system.
Well anyway i think this game needs more story quests with cinematic stuff while doin thouse quests and nice rewards.