There's a midsized number of experts in any given field.

There's a lot of people interested in a topic at a given point in time.

The experts will run from a tsunami of individual inquiries. Part of the role of a journalist is the act as a proxy for all that interest so that the experts' opinions can get out there without them facing endless messaging from every member of the public.

Now, one can argue about whether they do that job well or not. But that's a totally different argument than "I'd rather interact directly with someone who is actually an expert".