I'm not exactly sure what you're talking about, however mobile phones have awful bandwidth and awful browsers with not enough memory to cache everything they can.
In the context of websites, you also want the experience of new users to be the best it can be.
Basically, caching is nice, but it only works efficiently for applications that users visit often and that don't rely on links going viral, such as GMail. However, if you rely on caching for providing an acceptable user experience in cases where you rely on links going viral (such as Twitter), then you're screwed. Twitter has a mobile optimized web page that's much, much lighter than their desktop version and they did it for a good reason ;-)
Let me rephrase then; storing state in DOM may be ok for small pages with some insignificant JS on top to provide progressive enhancement, but from web app point of view its totally unfeasible and saving a few KB is IMHO not worth it.
In the context of websites, you also want the experience of new users to be the best it can be.
Basically, caching is nice, but it only works efficiently for applications that users visit often and that don't rely on links going viral, such as GMail. However, if you rely on caching for providing an acceptable user experience in cases where you rely on links going viral (such as Twitter), then you're screwed. Twitter has a mobile optimized web page that's much, much lighter than their desktop version and they did it for a good reason ;-)