All of the more recent ARM SBCs are capable of running as desktops for the most common tasks of browsing the web, watching movies, editing documents, etc... on less than 5W of electricity.
ARM's selling point is efficiency and cost, not raw power irrespective of cost.
edit: The real issue right now is not whether ARM can run as a desktop because it can. It lies in keeping the large number of devices and processors upstream with the linux kernel. Monitoring Kernelci.org shows that this is slowly becoming less of a problem as more enthusiasts become fans of ARM processors and the available chips and SBCs.
ARM's selling point is efficiency and cost, not raw power irrespective of cost.
edit: The real issue right now is not whether ARM can run as a desktop because it can. It lies in keeping the large number of devices and processors upstream with the linux kernel. Monitoring Kernelci.org shows that this is slowly becoming less of a problem as more enthusiasts become fans of ARM processors and the available chips and SBCs.