As far as investments go, treasures stored in heaven are the best deal, hands down. But, what better way to show your appreciation for treasures you have hear on earth, than giving back to God the partHe asks for (10%), and keeping Him in mind as you use the other 90. It’s all His anyway.
Why do we return tithes? Because God asked, He loves us, and we love Him. It’s that simple. After all He has done for us, it’s the very least we can do. See Malachi 3:8-12