As others have said, I think that the reduction in problems with newer models would contribute to a decrease in traffic. Further, already having so many threads and/or links answering most of the questions/addressing most issues is certainly a factor, as well.
One thing I didn't see mentioned, however, was ammo. Regardless of what Ruger and the gun writers they have bought off might say, the P3AT (not the Little Copied Pistol) started something of a 'revolution' in .380 pocket pistols and helped greatly increase interest in the cartridge by consumers. This resulted in an increased interest on the part of ammo manufacturers. There were already a few, good cartridges on the market that worked well in the P3AT but - over the course of a couple of years - several new loadings and some entirely new bullets/designs came to the market. Many of these had been developed almost specifically for - and tested specifically with - the P3AT.
Each of those new loadings/bullets, etc. sparked discussion. There were comparisons with the already existing ammo, comparisons with other newly released ammo, very helpful if 'informal' tests and so on.
Now, however, the development of new .380 ammo seems to have slowed a bit and most of us have probably decided on what ammo we want to carry. For those who haven't, there is a wealth of discussion, data and comparison already existing here and elsewhere on the 'Net.
As support for my hypothesis, one need only take a look at the current thread titles. Looking through the first four pages of thread titles, I see only two that are ammo-related, at all and neither of those titles pertain specifically to ammo performance. Instead, one asks about the possibility that the poster's chosen ammo is too powerful, possibly causing a mag drop, and the other asks if the P3AT is usually ammo picky. Other than a sticky with links to ammo tests (which saw its last activity in November of '09) there are no thread titles on the first four pages (which is as far as I looked) pertaining specifically to ammo performance, asking 'what carry ammo' or discussing any new .380 ammo. A year or two ago, there would have been at least two such threads in the first four pages. In fact, I'd say there is a good chance there would have been at least that many 'active' threads on the first page dealing with choice of carry ammo. ammo performance and so on.