Trivia: The Krite that grows to human size is usually obscured, shot from a distance, or only seen for brief instances. This is because the crew wasn't happy with the way the costume looked. While the Krites looked great as tiny creatures, once they reached human-sized, they looked unintentionally hilarious. The crew had to shoot it in such a way to make it feel like a threat without directly showing it too much. This is also why the Krites don't grow that large in any of the sequels.
Trivia: The name of the town in the film is "Grover's Bend." This is a bit of a reference to the town of "Grover's Mill," which was the town where the aliens supposedly first landed in Orson Welles' infamous "War of the Worlds" broadcast.
Trivia: One of the Krites is biting the head off an "E.T." doll. Dee Wallace coincidentally co-starred in both "Critters" and "E.T." as the mother of each film's respective young protagonist.
Answer: Maybe it's because they didn't have the budget where they could afford to do such an idea.
Rob245