The headshot photographer highlights the fact that they’ve worked with celebrities.
This is a marketing tactic intended to improve your perception of the photographer by impressing you with the fact they have photographed celebrities. Perhaps recently — or perhaps they are still promoting their brush with fame as far back as the 80’s or 90’s.
This is not in any way a guarantee that the photographs are good — so be sure to look beyond the celebrity and at the photographs themselves.
Many photographers who are in the business of working with VIPs and “high-end clients” do so almost exclusively. They are probably not shooting actor headshots for virtual unknowns — and if they are, then you can expect to pay a premium in the process.