Janeway should have gone bald. Several other power figures of the era were. Picard. Sisko.
Kathryn Janeway sent death back to hell without her, made fear itself afraid, spanked the Borg, deleted the Krenim timeship, and had the Maquis eating out of her hand like your granny's pet Pomeranian. She did not need to bow to the whims of Starfleet captain fashion.
Besides, the only bald woman in Trek canon was under an oath of celibacy. Kathryn decided that wasn't her thing.