It's true that the ground cloth really doesn't protect the pool but what it does protect is all the hard work spent getting the ground level. If you had to use sand to level the ground the cloth will protect the sand from hard rain and water from the pool. The last thing you want after several hours of laser-leveling and tamping sand is for it to erode and wash away. So, yes, while it's a bit too flimsy to protect the pool it at least protects the sand underneath the pool, especially when you've brought the pool inside, from eroding and washing away.
As for the product itself it's pretty flimsy. We've had the ground cover that came with our 16' pool for a couple of years now and it's completely deteriorated. Expect to replace it every two years if you live in the northeast and keep it out all year.