QStyleFactory.keys() not listing all available styles

Run the following from python 2.7 or 3.7

>>> from PySide2.QtWidgets import QStyleFactory
>>> print(QStyleFactory.keys())

[u'Windows', u'Fusion']

Here's the PyQt5 version:

>>> from PyQt5.QtWidgets import QStyleFactory
>>> print(QStyleFactory.keys())
[u'bb10dark', u'bb10bright', u'cleanlooks', u'gtk2', u'cde', u'motif', u'plastique', u'qt5ct-style', u'Windows', u'Fusion']