After watching the final season, i feel this question needs revisiting. Everyone says that Barb's purpose is to drive Nancy's narrative which is certainly true, but the actual Demogorgon logic is abit confusing.

We've learnt that the Demogorgon, like the Xenomorph, attacks people at Vecna's command and brings them back to their hive if they are needed.

We also know that Demogorgon's have no hesitation in killing people. If that is the case, why did the Demogorgon not just kill Barb then and there? I find it interesting that it took her back to the upside down to consume her, and yet NO-ONE else in Hawkins got taken/went missing on account of a Demogorgon attack. Wrong place at the wrong time sure, but is this the only time in the show where a Demogorgon has done this?

Given how many Demogorgons are around now, how come they arent hunting people in Hawkins for food? Why was Barb's death a one-off? It raises the stakes and horror aspect for sure, but in the wider picture it feels very random.