It lets him LARP as a 5d chess playing cyberspy. He thinks he's the one controlling people, making them spend days searching his new "clever" alias trying to get his identity. It also keeps the attention fresh, not that he needs any help with that. Given how little happens in Phil's streams and how empty his chat is, it's not like he needs to do anything to stand out.
I think it's part of the reason OIC is just so...bland as far as Phil's supporters go. E7 was actually mysterious enough to speculate about. BSV had a combative personality, Tut was fairly trollish, KG is a cursed spirit, forever bound to live in DSP's forum until he can finally pass into the afterlife by beating the detractors. Swaggins has the pathetically insecure thing, but OIC is just...there. Like, his big claim to fame is consistently throwing money at Phil under different accounts, which we've already seen plenty of times before. His biggest claim to fame is supporting the vest streak, but even then, people remember Phil wearing stupid vests and sending out beg tweets every night. The fact that OIC supported it is, at best, a boring afterthought.