Don't waste your time collecting too many leather; since leather is rather heavy and there are only a couple of relatively non-useful recipes that use it, such as tents, sailrafts, hammocks, and bandages.
A tent is most useful when playing on a large random island, where getting lost and not being able to find your way back to your shelter is a possibility. Also, since in the random island game there is the possibility of structure fires, a tent is a way to guarentee you have shelter when your other shelters burn down. Sailrafts are only useful on custom maps that include multiple islands and water dangers like sharks, since it acts as a storage building as well as a way to stay out of water while traveling off-shore. Bandages are useful if you don't restore from a save game after being injured, since they immediately stop bleeding wounds, but you can replace leather with a leaf for this purpose, and the leaf weighs much less.