Yes. They can pretty thoroughly ruin your physique if you let it get bad enough.

Pretty much every example you'll ever see of a physique that "proves" that "small" legs look fine is of some young athlete who probably runs sprints until he nearly pukes on a regular basis. Or some retard posts Arnold's "proportionally small" legs even though it only takes 5 seconds to find a video of the guy repping out squats with enough plates to bend the bar.

You don't need to sperg out training legs like an oatz and squatz spaz, but if you skip them with an image of a clean v-taper and athletic "thin" legs in your head you're actually gonna achieve pic related.