<p>Besides all the the more substantial reasons that are given above, of which I share most, if not all:</p>

<p>Sometimes, it feels <em>efficient</em> to help: Having the answer 90% ready in the form of parts of slides that I have used in teaching or an exercise I have asked implies that I can sometimes answer questions somewhat quickly.</p>

<p>Second, I get inspiration here for my own teaching, as questions are sometimes nice questions for my problem sets.</p>
