Why sow seeds in a straight line? Seeds are normally sown either in drills/lines or broadcast by throwing swathes of seed. Weeding is undoubtedly easier between neat rows as you can be more confident of distinguishing between weeds and seedlings. And there is more space to give your hoe a good shove.
But for less weedy spots and for gardeners with more time, throwing seed evenly across the soil can be more effective, particularly for root crops such as carrots, beetroot and radishes. The effect is softer and less regimented. A classic potager has a mixture of rows, patches of broadcast seed and plants climbing up hazel trellises.