The explanation is that distribution rights are sold by territory because most old school distribution channels are by territory. And content is usally financed by the sale of rights (usually before anyone has seen anything).
But streaming is becoming more and more important and those deals will be reviewed.
To give you an example, when Netflix opened in my country, House of Cards wasn't in the catalogue. That's a show produced by Netflix. But that was because Canal + Afrique held the rights. A few months ago, it was added. Most likely because the contract expired or because they renegociated.