* Practicality: Contact lenses, especially for a long-running film series, can be uncomfortable and disruptive. They can also cause eye irritation, especially if worn for extended periods.
* Aesthetic Choice: The filmmakers may have felt that Radcliffe's natural eye color was more suited to the character's overall appearance. They wanted to focus on capturing Harry's spirit and personality, and his eye color may not have been a central element in their vision.
* Subtlety: The film adaptation often takes creative liberties with the book's descriptions. The filmmakers likely decided that green contact lenses would be too distracting and detract from the story's core themes.
It's also important to note that, ultimately, the way Harry looks on screen is a matter of artistic interpretation. The filmmakers had a specific vision for the character, and they may have felt that Radcliffe's natural eye color contributed to that vision.
Ultimately, the choice to not use green contact lenses was a creative decision based on a variety of factors, including practicality, aesthetics, and the overall vision for the character. It's a testament to Radcliffe's performance and the strength of the film's other elements that Harry's eye color didn't become a major talking point for fans.