If anyone ever wondered why Lucita frames Titus for Valero's murder, Titus himself explains it.

The Azaro family has a monopoly on the military; they control the armed forces, which are their most powerful weapon, not to mention their Levies and provincial police. Furthermore, they are the family that historically holds the position of councilor of security and war, which also gives them power over the security forces in general.

Lucita, and by extension the Azaro family, dislike the Golden Guard because it is a security force over which they have no influence. The Golden Guard answers only to the king and its sole mission is to protect him and his family. Historically, the Golden Guard was also used for clandestine activities, such as investigating nobles from other houses and serving as the king's armed wing.

I believe Lyza didn't just discontinued the Golden Guard because they were too powerful, but because she feared that the Sazon and Azaro families would lose faith in the Toras and begin plotting coups against the crown if the Golden Guard continued down that path.