IMO, morality is descriptive, not prescriptive. It simply describes the majority of people's opinions on social issues at a specific time. As such, it has no actual use; it's more of an concept than anything.
Saying something is wrong because it's "immoral" only works if you are taking to someone who agrees with your moral code in that particular instance. Telling a serial killer that killing is immoral won't really achieve anything; to them, it may not be, or they just may not care (which is kinda the same thing).
Most laws, even those purported to be based on morality and ethics, have in their root a certain degree of logical reasoning to them.
Saying something is wrong because it's "immoral" only works if you are taking to someone who agrees with your moral code in that particular instance. Telling a serial killer that killing is immoral won't really achieve anything; to them, it may not be, or they just may not care (which is kinda the same thing).
Most laws, even those purported to be based on morality and ethics, have in their root a certain degree of logical reasoning to them.