Technically, in the United States, a a whitelist of approved Wi-Fi cards is required by law under 47 CFR §15.212(a)(2)(iv). A laptop manufacturer that doesn't implement such a whitelist is in fact in violation of FCC regulations and can be subject to fines and other penalties. — bwDraco 44 secs ago

Technically, in the United States, a whitelist of approved Wi-Fi cards on a laptop is required by law under 47 CFR §15.212(a)(2)(iv). A laptop manufacturer does not legally get to choose to not implement a whitelist; failure to do so is a violation of FCC regulations and can subject the manufacturer to fines and other penalties. (I am not a lawyer.) — bwDraco 4 mins ago

...and voting to close my own question (and in fact, I wish I could downvote it). At the end of the day, the answer is very simple: the FCC, like any government agency, only has limited resources, and it is far more efficient to require device manufacturers to implement restrictions against end users and take enforcement action on no more than a few dozen to a few hundred noncomplaint manufacturers, than to go after what may very well be tens or hundreds of thousands of noncompliant end users, some of whom may be very difficult (and expensive) to track down. — bwDraco 5 mins ago