Politicians often appear on T.V. as so-called "talking heads". A political program will invite two or three politicans from opposing parties to discuss a controversial topic, give their opinions, try to score "points" off their opponents.
You also see government ministers doing their business around the country and overseas. So there are photoshoots at EU summits or (for example) the Agriculture minister visiting a farm.
But the Speaker is meant to be above politics, so isn't invited as a talking head. And the speaker isn't a minister, so doesn't go to EU summits. The speaker does spend most of their time in Westminster, chairing the house of commons.
You do see documentaries about the role of the speaker, or the history of the House. Betty Boothroyd and Bernard Wetherill both appeared in such documentaries. Sometimes the Speaker might appear on non-political talk shows. Boothroyd, for example, did Desert Island Discs.