Yes, really. You'd be surprised.
1. Protecting a friends name
2. You don't want to get involved with a case (example: you see a crime, but you don't want them knowing you seen because you don't want to be involved
1. If you need to cover up for your friend in a serious situation, you might need new friends. Besides, it could most likely be obstruction of justice if its serious enough, which is a crime in itself and invalidates you being a law abiding citizen
2. Yeah because I totally don't want to see justice served. Also a possible crime if you refer to #1
Sure they might be valid reasons if you are a lazy person. Also, we don't live under fascism yet, so there isn't any outrageous criminal laws in which I would change my opinions on these