"I Don't Know"

I don't really understand why people tend to use the word " I don't know" or "How do I know"...

To me ppl who uses this phrases often is a person who are ignorance of a particular subject and the phrase "I don't know" is a lazy man's answer to everything...

If I gonna hear these two phrases again today...

I probably will go ka-boom as I already heard it for like dozens of times today...