That's because courts return a verdict of "Guilty" or "Not Guilty". Never a verdict of "innocent". There are long historical and logical and legal reasons why this is so.
Your post is actually not quite an accurate description of verdicts in criminal cases as given in Italy, under Italian law. This was discussed up-thread in great detail (perhaps more than many would desire).
Under Italian procedural law, there are FIVE kinds or specifications of "Not Guilty" (also known as "Acquittal") in final criminal trial verdicts. Some of these specifications correspond to the concept of "innocent" with regard to the crime(s) charged. These specifications are detailed in the Italian Code of Criminal Procedure ("CPP" being the abbreviation for this legal document in Italian) Article 530, Judgment of Acquittal. CPP Article 530 requires that the judge in the written operative judgment specify the kind of acquittal.
Here are the five specifications:
1. The crime did not occur.*
2. The accused did not commit the crime.*
3. The act of the alleged crime was not an offense under the law.**
4. The act of the alleged crime is no longer an offense under the law.***
5. The accused is a person who cannot be held responsible due to a lack of mental capacity.****
* Corresponds to the concept of "innocent" of the crime charged.
** The accused committed the act, but it was excused, for example, because it was self-defense.
*** The law was changed after the act happened so that the act is no longer a crime. (The significance of this provision may include that Italy's Criminal Code - the list and descriptions of crimes and their punishments - was written during the Fascist regime, and has been not been rewritten in total, but specific articles have been removed or updated to democratic standards since the end of World War II).
**** That is, the accused is either found to be insane, or perhaps, was a minor who could not be considered responsible for the act.
Italian law also includes the judgment of "dismissal", which when final has the effect a final acquittal, and includes the case when the statute of limitation of the crime has run out. Because Italian trials take a long time and many appeals are allowed - a verdict of dismissal because the statute of limitations has run out is not uncommon. There is, however, no statute of limitation in Italy for murder.