Why is it so hard to find "Lamb " meat in groceries in USA? can buy it safely on Amazon?

want to make indian curry with lamb meat...but my Wal-Mart near me doesn't carry it or any of the local groceries...why? THIS is really the best meat , even more than chicken to make curry with? why agree or not?
Update: HOW EXPENSIVE VS. CHICKEN? WHY? WHAT ELSE CAN USE? ROAST BEEF MAYBE?
Update 2: WHAT ABOUT ROAST BEEF INSTEAD? SINCE CHEAPER? HOW TASATE SIMILAR OR NOT?
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