If the disk the system is installed is encrypted with a strong password, and it is not shared between multiple users , is there any significant compromise by making the user/root password simple or reusing an existing password?

[TvO]

Title pretty much sums it all, but I will add a few comments:

The main benefit for using a more simple password for user would be convenience when password is required, such as when using “sudo” commands in the terminal.
In theory, this would be less secure, but how much of a compromise would this be on practice, if the system is encrypted?