Based on your description, it sounds like you probably live in your laptop. Other folks don't, and a hand-adjustable keyboard stand may not work very well for them. Imagine, for example, trying to raise something like that — even assuming it could take the weight — while using multiple monitors.
One would hope... 88-key keyboards are 45lbs (about twice a normal 27" monitor) and the older ones are significantly heavier... a non-POS stand should take >120lbs without a hitch.
That being said, there's certainly nothing wrong with a product better tailored for its purpose.
It's not just about how much weight the stand can hold. How well-balanced is it? How well-balanced is it while being raised or lowered by hand? Keyboards are typically fairly even in terms of weight distribution, and have a low center of gravity. Monitors, not so much.
Based on your description, it sounds like you probably live in your laptop. Other folks don't, and a hand-adjustable keyboard stand may not work very well for them. Imagine, for example, trying to raise something like that — even assuming it could take the weight — while using multiple monitors.