And they have so many (non-'original') where they only have a few series available at the end or in the middle. I don't understand the licencing/purchasing decision that can lead to that. Seems to happen far too often for it to be different studios/licencors, obviously that happens sometimes.

BBC's QI is one example. I understand new series not being available on Netflix (in the UK) as the BBC now have their own subscription platform. But it's not just that, because Netflix don't have the earliest ones either, just a seemingly random set in the middle, perhaps even non-contiguous.