Dry treatment is an extra coating that helps to prevent your rope from absorbing water in wet conditions. In addition to that, it also keeps the rope guarded against other cruds, which eventually enhances its lifespan. If your rope is not dry-treated and absorbs water, it becomes much heavier and hard to handle. In the long run, it also loses its strength due to the dampness.
The dry-treated ropes are best suited for alpine climbing, ice climbing, and mountaineering. However, keep in mind that these ropes can cost you about 50 percent more than non-dry ropes. So, if you’re more of an indoor climber or you’re not keen on climbing on a rainy day, you do not require a dry-treated rope.