Yes? For society in general, for professionals in criminal justice system and also to some extent even victim as well, it is lot harder when there is no motive.
Perpetrators without motive can not be negotiated with, punishment may not a strong deterrent, rehabilitation is lot harder. Economic crimes or crimes of passion or ones as a result of addiction can have a path to rehabilitation and recidivism can be solved by tackling the underlying issue like poverty, addition etc. Even solving crimes without motive can be harder as there is less assumptions we can make about the perpetrator.
