Well one reason is there are many many different legal jurisdictions involved that handle media distribution differently. Licensing and copyright agreements are all over the place. Most of this stuff predates the internet from what little I know, so you have the typical legal clash between the last generations rent seekers and todays.
Their documentaries seem to be subtitles in English, Polish, Spanish and Italian (in addition to the original French/German that is typical for all Arte programs).
So my guess would be it is made available for European Union only. Although you could argue that there are not many countries left in the EU whose main language is English.
Thanks for your help :) Unfortunately the Arte TV website is also region locked and doesn't let me watch this from South America. A shame, it sounded interesting.
Sounds like it's time to fire up the VPN with an exit node in a different region, er, I mean visit the region personally yourself. Yeah, that's what I meant.
Arte is a French/German public TV channel (excellent one in my opinion).
I guess this video is blocked outside these two countries (also available in Belgium, Monaco, Luxembourg, Austria, and Switzerland I think)
I absolutely hate geoblocking. There is no single reason I can come up with why it could be a good idea.