There is no reason unless you want it to act like the console...which I think Nebula, WinKawaks, and Final Burn Alpha, all allow. Mame I think you limited to Arcade mode only...but don't quote me.

The real AES will play MVS carts...with an adapter since the carts are two different form factors...however I'm not sure if MVS units will play AES carts...adapter or not.
Basically it comes down to whether or not you want to toss in coins.
Really I wouldn't be concerned with emulating the AES...now the CDZ...I would just for the improved audio...but thats a different subject.