Texture reducer is a Canvas+ exclusive feature. When your game targets all resolutions you need huge textures for iPad retina like devices and small textures for small mobile devices. A game developer has many ways to handle this:
As the texture reduction lowers the quality of the final images to be displayed, an interesting approach that we have recommended to some customers is to apply it only for certain device models, leaving higher resolution for some others (you can use the “navigator.userAgent” property to identify the device model). This, of course, it is not an easy task on Android due to the big number of device types, but on iOS is definitively an interesting option, specially for older devices such as the iPhone4 or the iPad Mini 1st generation.
Check out the API documentation.