The reason for not running pacman -Sy
is to avoid installing packages from different package database updates.
Example: It's 5 days later when you've forgotten you ran pacman -Sy
and run pacman -S nvidia
that you're likely to break something
source The bash script checkupdates, included with the pacman-contrib package, provides a safe way to check for upgrades to installed packages without running a system update at the same time.
see: System maintenance