I just realized why Riot keeps URF annual - and it's very sad.
Keeping URF annual despite the community's wants and desires is important for Riot to ensure a long lifespan for their only game.
We want URF
They probably want URF
But it's all about psychology. If we have URF all year long, more people will play all year long, and the game won't feel like it's getting these "surges" of life because of URF. It will be a happier, more fun game, all year round, which takes away the feeling of "wow, so fresh, so many people are coming back" that URF gives once a year.
Riot is required to make it annual against our wishes as a collective community because it ensures the longevity of their game.
It's terrible.
It's depressing.
It's the truth.