Because a company/org specific site for journalists doesn’t get the interactions with people outside that org but within the sector of coverage unless people do a lot of following of others.
But note also that the first one isn’t associated with a media organization but rather an industry sector.
You can use social.bbc to broadcasts articles that people want to read, but the “what is going on with the energy grid in the UK” will never show up in local there but rather over at mastodon.energy/ … and so that’s where the journalists are… though there’s still a lot going on over at twitter.com/search?q=%23energytwitter