Here's why:
* Meaning: "Merry" describes a state of joyful celebration or being cheerful. It's not something you can be *more* or *most* of in the same way you can be *taller* or *stronger*.
* Usage: We often use other words to express greater degrees of merriment, like "joyful," "delighted," "ecstatic," or "elated."
Here's an example:
* Instead of saying "He was the most merry person there," you might say, "He was the most joyful person there."
So, while "merry" doesn't have a traditional comparative or superlative form, we can use other words to express similar concepts with varying degrees of intensity.