The main reason for this is perhaps that this instalment was even more Japan-o-centric than usual - The first chunk of the episode in particular exemplified this with its talk of TPO, a frequently used Japanese acroynm meaning "time, place, objective"; in other words a broad comment on a person's given social situation. In short then, this segment dealt with inappropriate behaviour for any given situation, which of course with this being Sayonara Zetsubou Sensei was taken to the ridiculous (and not to mention amusing) length of playing dodgy erotic Nintendo DS games in the middle of Japan's "Warring States" period.

From here, we take in holidays that perhaps shouldn't be, pondering why Japanese prefectures who aren't directly next to water should celebrate "Sea Day". This soon melds into situations where celebrating can either be considered good or weird (celebrating a horse winning a race after 300 straight defeats for example) before introducing us to the concept of a "chimera holiday", which apparantly needs to be as boring as humanly possible. I'm pretty sure I've had a few of those actually...
Finally, we return to the concept of taking "excessive care" of things, from over-zealous copyright infringement lawsuits (oh, how I punched the air over that being mentioned, liberal despiser of modern copyright law that I am) through to the ever-increasing blight of health and safety (which sees the removal of all the fun things from a children's playground in this case). If the first two segments of this episode were a little too localised for your tastes, this is probably the one that had you nodding in agreement.
So, not a classic episode (particularly for the non-Japanese viewer) perhaps, but hey, if nothing else I feel like I've learned new things from this episode. And learning is a good thing, as we know, with your level of education only slightly less important in life than your ability to successfully complete the Sayonara Zetsubou Sensei drawing song without creating a monstrosity. That particular gag, which closes off every episode of this series, should probably be getting old for me by now, yet somehow it makes me laugh out loud every time.