I suspect that most people /do/ change it, once they become aware of it,
for the very reason stated in the comment above 'UMASK' in the
/etc/login.defs file:
<quote>
# UMASK is the default umask value for pam_umask and is used by
# useradd and newusers to set the mode of the new home directories.
# 022 is the "historical" value in Debian for UMASK
# 027, or even 077, could be considered better for privacy
# There is no One True Answer here : each sysadmin must make up
his/her
# mind.
...
UMASK 022
</quote>