If you're in a couple and one of you pays tax at a higher rate then, providing you trust each other, putting non-ISA savings in the name of the lower taxpayer could mean you'll take home more – as the lower taxpayer gets a higher personal savings allowance. Obviously, this only matters if the higher-rate taxpayer is exceeding their personal savings allowance.
P.S. For those who aren't married or civil partners, there's a tiny risk that if one of you died within seven years of doing this, that there would be inheritance tax to pay on it.