generally bench top drill presses are made to be set upon a bench. So 30 to 36" high - table top height. If you make it too high you will have trouble changing speeds and reaching up for the quill. If you make it too low it will be hard on your back because you bed over to see. You want the drilling to take place in front of your face just a bit below or else you'll have to bend over to see what you're doing.
basically the height of the supplied column is fixed, and the drill chuck is part of the head that goes onthe column so its height is fixed. Gnereally your drill will meet the work about 2-4" below the chuck and the chuck will extend 2-4" down from its resting point. So all this is fixed heights so that's why it needs to be on a bench-height stand.