In a lot of situations, the pointing and the bedding will crack under the ridge capping and this allows water to seep through the cracks and pond on the top edge of the roof tile that is upstream of the bedding.

If this pool of water is not allowed to escape (via weep holes), it slowly builds up and will eventually overflow the top edge of the roof tile. This is usually why a tile roof will develop a leak only after prolonged rain.

There are numerous ways to fix this roof leakage problem caused by the lack of weep holes.

Also, the need for weep holes is not universal under every ridge cap. We have a lot more information about needing weep holes for roofs on this website.