Why is using a HOTAS more stupid than using a keyboard ?

Unless you have a replica of a WWII submarine control room, any controller you'll use on a pc is good.
None will give you the immersion of a real life sub control room though.
So a HOTAS can be as good as a crummy old keyboard + mouse.
So to the OP that wants to use a HOTAS : go ahead, just program it so that all relevant controls are mapped to the different keys on the controller and you're good to go.