Why do we need emulated sdcard? Why is there an "emulated sdcard" in Android? I suppose it is located on the same internal flash memory (there is only on physical default memory, right? (excluding separate physical sdcards of course)) as Android itself, so why do I need to "emulate" it? Could we not just write to the "internal" storage?
Historically virtually all the early Android phones had a removable SD card and a very small amount of internal storage (by modern standards).  Apps were written expecting to be able to get access to the external storage and use it for data storage.  Then phones started shipping with more internal storage but no sd card and to keep these older apps working had to emulate external storage.  We now had the ridicules situation of real external storage with an sd card and emulated external storage being quite a common setup and some older apps not being able to use the actual real sd card.

If you were starting from scratch now and could ignore all the old software then things could be tided up but as it is it's a confusing mess for the consumer and the developers.