Right; my impression was that everyone loved it for the "drive to your gate" thing, although this was clearly more convenient before the age of security. Being trapped in the little gate areas with a full security line experience between you and reentry from any food/bathroom sprint is not pleasant and I never got why Berliners thought it was a worthwhile tradeoff. I was looking forward to making any future visit via BBI (got excited when I saw it pop up on Kayak at the idea that you could book a flight to an airport that wasn't even opened yet...a future airport, if you will).
I think, at least among former West Berliners, maybe nostalgia for the Cold War and not having to share infrastructure with the Ossis must play some role.
And I can actually see them liking the shitty Airberlin terminal because Germans can put up with literally any amount of bullshit (read: spending all day comparison shopping canned food prices at different supermarkets) to get a discount.