Name me a situation where this would be used as opposed to expulsion, censorship, or losing the office due to inactivity (as proposed in another amendment)?
It is possible to game an activity standard to avoid expulsion/removal from office, or to rely on legal loopholes to circumvent such as Bacon King did several times.
Having a process like this ensures that people can still take action and remove a Senator who is doing just enough to avoid removal but little else (phoning it in basically).
Though frankly most of Congress operates on a basis of phoning it these days comparatively speaking.