David Roberts tweets a lot, and is pretty entertaining and informative on various subjects, but he is bizarrely wrong on this matter (as to whether top sheets are useful, or not.) You could only conceivably hold the view that a quilt cover alone is better if you lived in a permanently cold bedroom. In Brisbane, everyone probably spends 6 months of every year sleeping just under a sheet.
The innovation that I want to see in top sheets for double, queen or king sized beds is to have them made so that there is a lengthwise split in the middle from the top down to about 60 cm from the bottom edge, and the two halves overlap by about 30cm. This would allow one person to use their side to cover their body and (say - because this is how I sleep) pull the top over their head without pulling off the other half from their partner's body. Sure, you could achieve this by just putting two single sheets on the bed, but the precise arrangement doing that is always going to be fiddly.
Perhaps I should check if this sheet design has been patented.
Update: gawd - Google patent search shows many, many patents related to sheets. One is about half way to my suggestion, but the split should be longer. A lot of people have thought about sheets over the years...