Because so much of the bbc website is http, today, in 2019. At least you now get TLS between the browser and the bbc server. Accessing bbc over Tor normally leaks cleartext http to the exit nodes.
The only other parts that remain HTTP (that I've seen) are certain archived content, e.g. the older Learning[0] and Languages[1] portals.
get "https://www.bbc.com/travel/story/20191021-the-sea-of-60-ghos... Location: http://www.bbc.com/travel/story/20191021-the-sea-of-60-ghost...
BBC is one of very few sites on my HTTP allowed list. By default I've disabled HTTP completely.