What is the most likely cause of short, quick, and useless reviews? My theoretical computer-science paper that I submitted to an Australian (i.e., located in Australia this year) B-level (according to http://portal.core.edu.au/conf-ranks) DBLP-listed computer-science conference was accepted 4 weeks later, but the reviews are short:


5 sentences (accept)
2 sentences (accept)
3 sentences (reject)
3 introductory sentences + 3 sentences noting weak points + 3 sentences noting strong points (borderline)


All four reviews are superficial. They partially contradict each other. The buzzwords and phrases that occur there are: well organized, good presentation, minor format errors, sound results, no theorem proofs, highly relevant, well written, convincing, weak motivation, no empirical study, no clear justification of the contribution, only theoretical analysis, no explanation of contribution, no clear structure, results useful for practicioners and theoreticians.

There is nothing beyond these high-level claims in the reviews: no page numbers, no section numbers, no quotations, no citations, no related work, no examples/counterexamples. None of the reviews substantiates any of its claims.

It's the first time I get this kind of reviews. Usually, I get longer and deeper reviews that show that the reveiwers understood the technical contents of the submission at least a bit beyond the abstract and that elaborate on a technical level at least a little bit.

My questions are:


What is the likely cause of such short and useless reviews?
Is the conference really serious? (The paper submission site stayed open long after the formal submission deadline.)
Are my concerns groundless? Is what happened normal for B-level Australian conferences?
Is there any way to extract more information, say, by writing the PC chair(s)? If so, how do I formulate the message, or even what do I ask? Or is it better to keep silent and be satisfied with acceptance?


The proceedings will be handled by IEEE Conference Publishing Services.

I know that the exact answers might be hard to tell, so I'd be happy with answers based on well-informed guesses.
The basic idea is simple: reviewers have no incentive to write good reviews apart from their desire to see the conference succeed. Seeing an abundance of short, superficial reviews with a high acceptance rate indicates a low quality conference. 

An alternative explanation might be that this is a non-archival conference, often referred to as a workshop. In that case reviewers mostly care about the general problem the paper presents and whether it sounds interesting/relevant. Program chairs are usually those who go through the papers to see what fits (and there’s a small number of submissions).

If it’s not a workshop, the program committee/organizers aren’t well-respected researchers, and they charge you a lot of money in registration fees, I’d consider retracting.