useradd not asking for a password?
Solution 1:
It is better to create new users with adduser instead of useradd. In this way you won't have this problem.
Solution 2:
to set a password for the new user I ran
sudo passwd testuser
Solution 3:
you can set the password with the root user after creating the user
root@yourpc:~# sudo passwd username
don't forget to run it on the root user. or you can just create your user with adduser that asks password itself.
For some reasons like -gid you might need to run the first command.