IMHO these are only gimmicks, that uselessly complicate the things (see where the internet went so far? even the simplest pages suck 3-4Mbytes, while a pure HTML would have costed you only a few kB (some 1000x less)), and thus makes both the eReader and the editing software more prone to errors than before. Let alone debugging one. It would require more resources, more space, more CPU power, more battery, more more more ....
