Personally, I think there are only 2 advantages (over something more polished like OS X):

i. Doomsday scenario: Competing platforms do something awful like direct spying on users, making it unaffordable/inaccessible or generally taking terrible, permanent decisions. Then, a free/open source OS will become The only feasible option. The counter point to this is, competition ensures very few companies will take that route.

ii. Learning & contributing: As a developer, I can understand and improve any part of the stack. Counter point: This doesn't address non-developers, who are a majority in today's world.