Who said we did? Stars would work fine without helium. Of course, Big Bang nucleosynthesis converted ~25% of the universe' hydrogen (by weight) to helium, so stars inevitably form with a large amount of helium. But it's not "needed".
It's not needed but it is part of the history of our universe. The stars in our universe would have formed slower if there was no helium around and the universe today would look very different if there had not been a small quantity of helium, but no, it is not essential to star formation.