Why would they make bows and spears, but not guns? That seems a fairly arbitrary technological line to draw.
Tyrants hate that.
Before firearms the world was mostly ruled by "nobles" (i.e., those who had extorted enough from the peasants to afford weapons and armor, and had the free time for the required years of training).
Now, it isn't. That didn't happen because the "nobles" suddenly decided to turn into nice guys.
Oh, buddy, do I have some news for you
Small scale 'war' should also be avoided. Guns make personal conflicts much more deadly.