There are two factors here. The speed with which products get reviewed. (Time of product launch to time of review publication.) And whether a brand/product gets reviewed at all.
The frequency with which Musical Fidelity appeared in the pages of Stereophile a few years ago was a running joke in the audiophile community.
Meanwhile, try searching for reviews of PMC speakers in those same pages.
Partly it has to do with company policy, partly how well a foreign company is represented in the US and what kind of PR campaign they sponsor, partly on reviewers' individual preferences, partly on kismet, and probably 3 or 4 other factors as well.
In short, it's hard to read anything into the patchy coverage other than it's undeniably patchy.