Everyone with an online presence already has a personal brand, in the sense that people form an impression from whatever they find. Personal branding is the choice to shape that impression on purpose rather than leave it to chance.
It matters most for people whose name carries the work: founders, executives, athletes and creators. For them, a personal brand opens doors a company page cannot, from speaking invitations and partnerships to talented people who want to work with them. It also outlasts any single role, which is why it pays to build it early and keep it honest.