Why cloud-based desktop concept(s) are not well applied till now?

Why cloud-based desktop concept(s) are not applied to Windows or smartphones till now? For ubiquitous quick data and higher background/setting accessibility, cloud-based desktop should be a star of the near future. Having said that market niche, add-on apps could simply be devised by software company as OS supplement to realize cloud-based desktop concept(s) ASAP to enjoy possibly a priority patent.