Probably because Aperiotic vents for the most part only help make the box look larger to the driver. they don't really contibute to the total SPL.
Most of the DIY community cares little about the total box size, i.e. sonotube subs, and/or will make the larger boxes needed for a textbook sealed design. many are only looking at bass extension and desire the extra low frequency output created by a tuned port design. With the exception of Rythmik subs I don't think that anyone here has made a sealed sub lately. Which is where the aperiotic vent fits best.
Also the aperiotic vents would require tweeking that many either don't understand how to accomplish, or simply don't want to fiddle with to make it sound correct.
I imagine if someone created a "how to make a diy aperiotic vent" whitepaper and published it here on the forums, or if the popular box estimation tools included apreriotic vents, you may actually see more of them created.