A big reason is that you work at the same company working to the same goals. Your "job" is probably more than just answering contextless questions.
A questioner asking "how do I get all of the emails from the production database?" certainly does warrant some additional probing and "what's a regex for valid emails?" might need a "don't do that, we need the validity of emails to be consistent across services even at the expense of correctness so..."
Admittedly when I was writing this I was thinking about the rather narrow case of answering questions on IRC or forums or what have you. Volunteer stuff. It does get substantially more complicated when your job depends on them getting to the answer.
A questioner asking "how do I get all of the emails from the production database?" certainly does warrant some additional probing and "what's a regex for valid emails?" might need a "don't do that, we need the validity of emails to be consistent across services even at the expense of correctness so..."