U.S. savings bonds (Series E & EE) have been a popular investment for a long time. While they accrue interest, taxation of that interest is usually deferred until the bonds are cashed. If a bond is titled jointly with another then, upon the death of the principal owner, that other can have the bond reissued in his name and continue to defer taxation. He can also choose to have the bond reissued with another joint owner, creating the possibility of continuing the deferral of taxation almost indefinitely.
An E or EE bond that is titled solely to someone who dies is included in his estate and the income tax on accrued interest usually paid by the heirs. Often those heirs are still employed, and pay taxes at a much higher rate than the deceased owner had. Tax law provides a solution for that.
Even after the owner dies, it is possible to include on his final income tax return the savings bond interest that accrued while he was alive. Thus that interest can be taxed at his lower rate, saving the heirs money.