As with most things, you can blame The Oatmeal http://theoatmeal.com/comics/mantis_shrimp

If I were tetrachromat I would keep mantis shrimp as a pet.

I wonder what university press release lies under the several stories with very similar wording that were published at about the same time last year. I note the submission here is at best a linkbait copy-and-paste of an article that originally appeared in another publication.

Simple, it makes a great headline and linkbait. I've seen this story reposted and rewritten over the past week all over the internet.

I think it's because people still think that this is esoteric and fiction, although scientifically proven.

Btw. only women have this ability. I believe the function of better eyes is to protect from predators or men, by differentiating more types of shades and therefore recognizing motion a lot earlier.

That last statement is wildly speculative. More likely is that it's because some key genes are present on the X chromosome but not on the Y chromosome. The same reason colour blindness is much more prevalent in males.

The real reason is that these genes sit on the x chromosome, which makes it possible for women to be heterozygotes. If one of the receptors is mutated and color-shifted, then women will be homozygous for the wavelengths of two of the three receptors, but heterozygous for the remaining receptor, which gives her two more wavelengths to interpret. Therefore, she will have a four-dimensional color space. A male with the same mutation does not have a normal copy of the gene, so still only sees three-dimensional color, with the third dimension different from what most of the rest of us see, which manifests as a type of color blindness, since the rest of society has engineered the world for normal RGB people.