Specialty Grains with Extract

Do they serve much purpose with an extract recipe?

they add complexity to the beer that you won't get with just extract alone.

Most extract recipes will almost always include specialty grains.

To say a recipe is Extract vs. Extract with Specialty Grains is kind of absurd. Even if you design recipe that is 100% extract, the extract itself will usually contain some portion of carapils or other cara- malts through the original processing of it. Your exceptions will be Pilsener and Extra Light extract. Pilsener extract is typically 100% pure Pilsener malt. And Extra Light Extract is usually 2-row with a small touch of Carapils.