When Bayonetta summon the infernal demons why do they need a conductor like the hair like why the real deamons don't just come out from hell?

i think they are one being, there is no real counter part

Well I could be wrong but oh to hell with it, the Umbran Witches hold their power within their hair, so as Bayonetta is an Umbran Witch her power lies within her hair as well and she uses it to summon these demons due to that being where her magic lies. I hope this is a good answer.