Competition tends to breed higher standards. Men's darts has been popular for a few decades now, but the increased level of competition has seen standards explode recently; each new star raising the bar and forcing a response from the rest. There are also more competitions and more top players than ever before.
Competition in the women's game isn't nearly so intense, and participation not nearly so high. As a result, you would expect standards to be lower. In principle this could change as more women start competing and therefore demand higher standards; in practice, it's probably always going to be true that women's darts is going to lag behind men, because I don't expect it to ever become high-profile enough.