I can very well understand your situation and therefore it is good that you raise your voice by doing a feature request! Apart from Windows RT, there are many more platforms and users who are not adequately covered by the current product offers of SketchUp.
The request for a Windows RT version of SketchUp has two challenges:
Windows RT runs on ARM, a processor that understands different instructions than classic applications (x86) are built with. Due to this, Microsoft didn’t intend classic desktop applications to be ported, and blocks running them (you can unlock this). Additionally, they favor to redevelop applications using the new frameworks (Modern UI) that target in one beat both Windows 8 / 8 RT.
On the other side, marketing people and product managers take a look at market share. I wouldn’t dare to guess if and which platforms are most likely to be targeted next. With the aim to build “native” apps, SketchUp ran out of puff already after only the couple iOS+Android. It costs significant effort to do more for little gain. Much more sustainable would be a strategy to cover every possible user (which automatically includes iOS+Android) at at one blow, by using cross-platform standards with priority.
For point one, a work-around for running (ARM) desktop apps is to “jail-break” the device. Using an emulator, some people had success to run x86 applications.
For point two, take a look at SketchUp’s web viewer that is contained in 3D Warehouse (but not yet stand-alone, nor offline, nor with modeling capabilities). Another commendable example are websites like SketchFab, they put web standards as first-class citizens. Much more could be achieved if people request pushing SketchUp’s web version, instead of asking for native ports to exotic platforms.