One possible reason for this is that using English is discouraged inside of France both as a culture and by all kinds of funny rules and regulations.
Another reason is that France had a headstart over the rest of the world with a system called MiniTel which gave pretty much one in three French households access to a service with a lot of the functionality of the early days of the net but on a system run by the French telecommunications monopolist. When the internet and the web became popular the French lagged behind because what they had was good enough to cause a lot of them to stick to what they had (a French system for the French available everywhere versus a system that was mostly geared towards the English language users). For the rest of Europe there was no such alternative (Local variations did exist but were not as successful and widely adopted as minitel was in France).
Finally, due to labor legislation France has one of the worst environments to do start-ups in.
Taken together that should explain some (but probably not all) of the reason why France with the exception of Paris is a little dark on that map compared to the rest of Europe.
One HN'er that I know lives in the South of France actually commutes to London for work, that's how anemic the tech scene in France outside of 'la banlieue' is (that's French for 'the suburbs' which they use to refer to suburbs in general but specifically to those surrounding Paris, inside that border is where most of the French tech scene is located).
Possibly someone from France can jump in here and give some more background and/or correct me if I'm wrong.