So? Hipster is one of many "uniforms" a person can choose to put on. It's a big symbolic difference when the person chooses it themselves versus when they're told how to look by their employer. Wearing a suit to work generally implies the latter (and that's not an unreasonable conclusion to draw, since it still works that way in a lot of fields outside of tech, and worked that way historically).

Certainly at my workplace I see all kinds dress styles.