In this case it's all about the look! Keyboards can also be made with a solid brass/stainless steel base, in which case it's about the weight which often affect

In this case it's all about the look! Keyboards can also be made with a solid brass/stainless steel base, in which case it's about the weight which often affects feel, acoustics and overall "heft" of it as an object. Past a certain point, people make things out of cool materials/heavy just cause they can.