Is training abs necessary to get a sixpack?

I've heard a lot "abs are made in the kitchen". I train abs 2-4 times a week very briefly with 2-3 sets of leg raises each time.

I can plank for about 90-120 seconds.

I have only a four pack and love eating some good food and drinking some beer one a week. I have no intention of going back to obsessive calorie counting routines.

Is my abs workout sufficient and is the reason I don't get a more defined frame simply a matter of body fat?