People who ask quick questions on chat almost invariably could have found the answer with 20 minutes work. Answering those questions frequently costs the answerer more than 20 minutes of flow; interruptions are costly to focus.
A while back, while working in a relatively large but sparsely filled open-plan setup, I had a tendency to hide in the far corner of the building when I had code to write. My manager at the time once complained "I start walking over to see you, but when I'm half way there I decide it's not important". I think he did, at least, pretty quickly realise what he was saying.
Having a (low-ish, but meaningful) transactional cost to "quick questions" is a good thing.
