Here's why:
* It's not standard punctuation: The standard punctuation mark at the end of a sentence is a period (.), question mark (?), or exclamation point (!).
* It doesn't have a grammatical function: There's no grammatical rule or meaning associated with using a "b" at the end of a sentence.
Possible scenarios:
* Accidental keystroke: The person might have accidentally pressed the "b" key instead of the intended punctuation mark.
* Incomplete thought: The writer may have intended to add more to the sentence but forgot to finish it.
* Internet slang or shorthand: In some online communities, "b" might be used as a shorthand for "be" or "because".
If you encounter a "b" at the end of a sentence, it's usually safe to assume it's an error.