A 70-200mm f/2.8 is mainly valued when you need both speed and flexibility.

The big advantage is the constant f/2.8 aperture: compared with an f/4 version, it gives an extra stop of light for lower-light shooting and can produce shallower depth of field. That matters for sports, events, photojournalism, and other situations where subjects move quickly and you can’t easily change position.

The zoom range is also a major benefit. In fast-changing scenes, a zoom is often more practical than a prime because you can reframe instantly without swapping lenses or losing the shot.

Its size and weight are largely a physics issue: a 200mm f/2.8 lens needs a large aperture, and a professional zoom adds more glass, corrections, and often image stabilization, so it ends up heavy.

So yes, it is especially popular for sports, action, and low-light work—but not only that. It’s worth it if you need telephoto reach, quick reframing, strong subject isolation, and good low-light capability in one lens. If your priority is travel convenience and you don’t need f/2.8, a lighter f/4 zoom or a prime-plus-midrange setup may make more sense.