I made some research, because this Lich matter bothers me. So I checked how Lich and alignments goes together in D&D settings from where this system has borrowed at first place. I found this:
"Alignment
Depending on the method of becoming a lich, a lich can be of any alignment, retaining whatever alignment it had in life.
Liches are mostly evil but there are references to good liches.
The reasons for good beings to become liches are limited but most of them come down to unfulfilled quests in life, guardianship over ancient evil and the oversight of future generations.
The process for being a good lich is more difficult to discover and in many campaign settings does not exist at all. In general, the process of becoming a lich has very evil requirements possibly making it hard for good people to retain a good alignment."
So it seams that good and neutral liches are possible, if we examine D&D, but really rare. Okay this helps me to understand more devs idea, even to most people liches are only pure evil creatures. That is the way how I have seen those described in every other fantasy game, movie or literature. Still weird, but somehow acceptable.
EDIT: Typo fantasy -》 literature