Here's why:
* "Hi" is already an informal greeting. Adding an exclamation point emphasizes it further, potentially making it seem overly friendly or even aggressive.
* Context matters. In casual, informal settings with close friends, it's more acceptable. However, in formal or professional situations, it might be better to stick to a simple "Hi."
Examples:
* Informal: "Hi! How are you?" (Acceptable with close friends)
* Formal: "Hi, how are you?" (More appropriate in professional settings)
Ultimately, the choice is yours, but consider the context and the desired tone when deciding whether to use an exclamation point after "hi."