One or more players are doing this dungeon for the first time.

[Uhm]

Sometimes there is little time to ask any questions. If the rest of the party rushes ahead as quickly as they can through the whole dungeon - then if I were to stop and spend 30 seconds to write a coherent question I would be far behind the rest of them.
With groups that take a more moderate pace this not much of a problem - there will be pauses long enough to write a question - but with extreme speed-runners it is a problem.

Yeah, that's the thing, when someone doesn't even have the time to ask I won't have the time to explain either, at least when there was never a question and nobody waits for an answer. If two people wait the rest should wait too, if only one stops the rest will run past. Surprisingly people often don't even see the need to wait for Haler/Tank and pull anyway, so when I stop without anybody telling me to it would be my fault if someone died. In that case it can't be helped that's why DF often sucks. Unless you like speedruns.