There are typically two reasons boards are stored on the hard (land stored) in a cradle system. First, like my first boat, if you live in a cold climate, the boat has to be taken out of the water in the winter time, so that snow and ice do not cause damage to the hull.
Second, is to store the boat on the hard, to do service work on the boat. This is more common for temporary repairs. It is much easier to do work on the boat, especially if it is below the water line, to pull the boat out of the water, store it, and work on dry land.
However, if the boat yard you are using, does not put the boat onto the cradle correctly, it can cause warping or damage to the hull. Here is why…
Boats need to be placed into a cradle system, with the palm of the stand, (the part that touches the boat), located at a strong bulkhead location. Some boats have these locations marked at the deck joint line, others are noted by examining the interior of the boat to determine where the bulkheads are.
If not placed on the cradle properly, the weight of the boat will put too much pressure on the cradle, and the palms of the cradle stand will damage the hull, warping it or causing surface cracking. Most of the time, if the boat is stored for only a short period of time, 30 days or less, damage is not caused. However, if you are buying a boat that has been in its stand for a long time, you need to check to see if the cradle is supporting the hull at the bulkheads, otherwise, you could expect damage.
On a separate note, I just want to mention that my boat received some keel damage after being hauled out once. The yard placed the boat on the cradle, and typically, blocks of wood are placed under the keel between the bottom of the keel and the ground. This is to help support the boat from the heaviest and deepest part of the boat. The boat was placed in the cradle incorrectly, and cracked the keel. It wasn’t significant damage, but did require about a weeks worth of grinding, laying up fiberglass, and re-painting.
Once the hull gets warped from this poor storage method, you may not be able to fix it. Thus, leaving the hull of the boat permanently warped or damaged.
Again, this can be expensive to repair, especially of the boat has been sitting for a long time. Boats can sit in shipyards for years sometimes, as owners do not want them in the water, if they intend not to use them, or if their lifestyles change.