Why should Mary Beard have to change her style just because she is in the public eye? She is not a professional broadcaster or in any other job where appearance is part of their job.
She is an academic whose main occupation is teaching and research at university. At some time she has attracted a programme makers attention, and from there his choice of her has been shown to be inspired by the way she rapidly became a frequent and popular broadcaster, but broadcasting is not her career and after all the identikit blonde presenters we get on tv and everywhere else on the media, it is nice to see someone who s content to be herself.
Let's face it, when male experts appear on tv looking like unmade beds, everyone thinks it great a sign that they are geniuses. That should apply to women as well.