Why does Android use fuse for internal SD card mount? The android ICS or later version(JB) use /data/media directory for internal SD card, and use fuse for mounting the emulator internal sd card device (/dev/fuse).

As we know if we use fuse, the files access have to communicate with userspace with low effect, why android do not use a stackable passthru filesystem such as wrapfs(wrapfs.filesystems.org) to mount the /data/media direct to internal sd card path(/storage/scard0)?

Especially, we have the MTP option access internal sdcard and external sdcard for PC(windows)
MTP is using the FUSE filesystem to access the sdcard while the OS is using the sdcard as well. The FUSE filesystem also manages permissions for the files stored in the /data/media folder.