PHD school was supposed to be a place for "Serious discussions about serious issues surrounding science, humanities and philosophy".

So why don't see many serious discussions about any of those things, but mainly of questions about doing someone's homework, people asking whether they should pursue their PHDs or even about how to pursue a PHD?

I supposed this section is rather general, not much into research or serious discussion.

It would be wiser to be more general to encourage more discussion. How many postgraduate do you see? Perhaps 10%? Many are befuddled whether to further or not. In most cases, once they are in their respective fields, they would opt for alternatives, which I believe would be more case specific.

But, of course, this forum is open for discussion, but how many would be sharing the same issue as you do? Very subjective.

Or perhaps people do not actually want to discuss them because they were pursuing something not worthy of discussing.

Not easy to indulge into very specific nature of one's research area. On general term, it's easier to have a discussion.