I also discovered that I couldn't use my Canon SLR to record more than 30 minutes of video continuously. The problem however wasn't Canon, but that I lived in a region (EU) that would have imposed a customs tariff on cameras that could do that, but by keeping it under that, the camera would be classed as a 'stills' camera and so was therefore exempt. Admittedly this is different from the case in the article - but it…
It would likely overheat anyway hah. Old Sony cameras have the same restrictions.
In short, there is no good reason anymore, but originally this was because of EU import tarifs.