Well…some reasons :
1)The percentage of french people speaking english is way lower than in scandinavian countries and Netherlands. It’s significantly lower than in Germany
2)Until some years ago at least, for some reason, France was the western country with the lowest number (relatively to the population) of home computers. Even more true for internet access.
3)As stated above, French people have been using the “minitel” for twenty years or so. It’s certainly way less performing than internet (basically it didn’t change since the early 80’s), but people are accustomed to it, and also it’s sufficient for the basic needs of many people (like finding a train schedule, or, as mentionned, having a sex chat). Also, these terminals were handed for free and immediatly usable, while one has to pay for his computer, find a provider, understand at least at a very basic level how a computer works, etc…)
That said, if one spend some time on a french speaking but international chat (like the french rooms on yahoo.com), it’s obvious that Quebecois are, if one takes into account the relative population of France and Quebec, way more present than french people. Though perhaps it could be explained by french people actually using french chats (but on the other hand, Quebecois probably use Quebecois chats too).
Personnally, I’ve been surprised by the lack of japanese people online. I saw more Chinese, Iranian, Indonesian, etc… people than Japanese people. Which surprises me a lot, given that Japan is a rich country with a large population. How comes I see more Iranians online? It puzzles me…