I do as well. The BBC actually produces a lot of these types of documentaries but they are probably not sold to broadcasters outside of the UK. I presume it's because they lack the big-budget, glossy look that is attractive to bigger audiences (and to international broadcasters). Or sometimes documentaries are trimmed or edited for international audiences. (I don't know if this is the BBC editing the programme or the broadcaster who bought the programme.)

A lot of the "old-school quiet" documentaries can be found on BBC4 - a specialised channel that shows programmes on specialised or niche topics.