Why are the reasons for some rejected submissions left blank?

It could be a slight technical glitch by the website (happens sometimes). Or, the user had run against the terms of regulation set by AB and was rejected, so the submitted answers got left blank, without any reason whatsoever. The moderator/reviewer might not want to spoil the AB atmosphere with purgatory terms, and to remain professional and clean, so he did not state the reason in case of corrupting one's mind with dirty thoughts, so he or she didn't provide a clear reason for the omission. But, some rejected submissions is unnecessary, so there is some gray area in specific parts which needs explanation and weren't given.

There are many reasons.

A few might be:

-Technical Glitch

-The rejection question or answer itself is good enough (as in self-explanatory)

-Or a user has submitted several
questions that are all being rejected for the same reason (i.e., they don't
meet guidelines) and it is redundant to type the same thing over and
over again.

The answers above were from the staff (albeit with a few modifications). An answer I have:

Sometimes, when an answer is inappropriate on the carnal level (i.e. makes someone squeamish, etc...), they may be rejected with the reason left blank as well. Sometimes, they still are even when put in the right category (for example: AB4Adults), because some questions still gross out adults.

If so, then an Answerbag question reviewer might not want to express how grossed out he is by that question in order to maintain the professional atmosphere in user-to-moderator relations so he leaves his reason blank instead.

In fact, this rejected question here was given a blank reason (and I wonder why ;) ) ***WARNING: Graphic question. Viewer discretion is advised!***: http://www.answerbag.com/q_view.php/14873

You see? That's in the Adult category but was still rejected, and without reason.