Documentaries - and speakers

Sometimes I turn on the TV in the middle of a documentary and it's annoying not to know which talking head is who. Even if I've watched the documentary from the start, my over-full mind can't always keep track of them all, especially when the documentary keeps cutting back and forth between them.

So why is it that they only display the name and position of the speaker only once, the first time she or he is shown on screen? Why can't they display that every single time? If it wasn't a distraction for the viewer the first time, it won't be the next time; in fact I find it far more distracting trying to remember who the current talking head is and what they're supposed to be an expert on.