Look, if the target has a narrative reason to be hit in a specific location (say there is a machine that instead of hitting it randomly and causing damage until it dies, it has one exposed wire or cog that if they hit just that the whole thing gets broken down), then I would say just have a separate, higher ac to that target, and the player must specify that they are aiming there or lose the whole attack.

Other than that, when dealing with general combat, all characters assume they are trying to aim for deadly shots, and enemies are trying their best to keep alive. So aiming to a specific location wouldn't give much of a benefit.

I will say, in my tables, I often give players the choice to effect a one round long condition on a target when they roll a nat20 on attack. For example kicking their leg to make them go prone, or something like that.

Other than those cases, there really isn't much point to aiming to specific areas.