See where Roblinator is in that picture above? The bank is just down there /points. Yet I have called Gobber more than once while just a short distance from a bank. He only hangs around for a minute, has a half-hour cooldown, and I might need him when I'm questing a few minutes later. But it's all about the instant gratification of not having to travel across a city.
My blood elf mage who is also a scribe is constantly needing to hit the bank or the AH while grinding up Inscription. She has to rocket across Silvermoon City to restock and then get back to the Court of the Sun to buy supplies and train up. But she never scoots back (rockets can't fly in Silvermoon, as you probably know). No, she uses up a rune and ports back to the mage enclave and then just bops down the ramp to the inscription room.