Smaller diameter lines give anglers a couple of key advantages. They are easier to cast long distances. You can also fit more smaller diameter line on the spool of a fishing reel. This makes them a great choice for fishing lures like topwater plugs, crankbaits, or other baits that benefit from long, accurate casts. Smaller diameter lines are also great choices for fishing near the bottom in wind and current, where the action of moving water creates drag on your line. The thicker your line, the more drag gets created, and the harder it becomes to keep your bait in the strike zone.