Since G give very very high score for key word show up at domain.
No, they don't.
Please google the words "apple", "orange", "pineapple" to see what is in common at top ten positions. I guess that is why people ask big $ for single keyword domain name.
Correlation does not prove causality...
"A" and "B" occurring together does not prove "B" causes "A" (nor vice versa).
"At the Cardinals game last week, about 75% of the folks wearing an Albert Pujols jersey were drinking beer. Therefore, drinking beer causes Albert Pujols jerseys."
Ridiculous? Those who say having a keyword in the URL creates high rankings for that keyword are making that same argument...
"In the SERPs, about 75% of the top ranking sites have a search keyword in the URL. Therefore, having a search keyword in the URL causes top rankings."
Jill, OWG and others are saying that there are other factors that cause keywords to often appear in top SERP URLs. I tend to agree.