Abs play a good part in locking the core for heavy stable lifts in my opinion.
Legs or no legs for stability.
I agree that as a person starting out that they do develop fine with other compound lifts.
As you move into advance you may want to hit them for a direct w/o for them.
I like the Hammer Strength Machine, weighted ab crunches and the Lat pull down for weighted crunches.
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