They Don't Last Long, But They're Easy to Replace
Yes, they're thin and warp under extremely high heat. Yes, after a year or two they pit and the plating chips off, then they rust, and you've got to heave them. But they're so cheap that replacing them is not painful. Their chief advantage is that these thin grates stay out of the way of radiant heat from below leaving the surface open for real searing. They're the next best thing to no grill grates at all. Alas, the only love they get is from this Meathead.
To upgrade the grate that came with your 22.5" Weber Kettle, pick up this cheap nickel-plated steel hinged grate. The hinges let you easily add charcoal for long low and slow cooks. Just lift the flap and drop in coals. No more fumbling to lift up the whole grate only to have your meat slide off and onto the coals. Yuk. They are also perfect for adding coals to the Slow N Sear, something you must do on long cooks, and it even works with GrillGrates which are cut to leave room for you to lift the hinged sections.
If you have a Weber Kettle, I strongly recommend you upgrade to these hinged grates so you can easily add more coals and wood.