Because it reads the master file table (MFT) directly from NTFS file system.

There is no limitation to using it.

Unlike other similar apps, which usually only offer single view, this app offers multiple views.

WizTree is faster and much more accurate than all the others as it properly handles hard linked files (doesn't count them more than once) so the total allocated size reported by WizTree will actually match the space used on the drive as reported by Windows.