Not everyone can decide which side to choose. Some people meet the membership requirements of neither 'club' or have no desire to join either. Not everyone is cut out to be a paragon or evil, many of us are just meant to be us and do what we are able...
Some just make up their own side and their own agenda.
That is not to say they are evil nor can one say they are good, not entirely. Simply they do not work for Lucifer and they do not (directly) serve God. Some might have seen the conflicts over time and realised that humans are the only ones who suffer, those who gain seem to never reveal themselves. Some are champions of what they consider to be Good and see the others as unjust, unfair or excessively demanding. Whether they are right or wrong in our opinion is irrelevant because they only listen to their own opinion.