I think you’re right, and like other people said “the tent” has become a sort of icon of the series.

I think it’s also from the “art direction” point of view, it also makes it appear as more of a “pop up contest”. They’re not going to an established venue, they’re saying “and here we are today at (location) for the British bake off!” It makes it feel more like a travelling “festival style” event like a local baking competition than a hard “we brought challengers to the Bake Off Challenge campus”. It feels more approachable when it looks like it could be “in your back yard” than in some far off studio.