Most people think of holes in roofing material as the cause of leaks. While the main roofing material used (metal, tile, and so on) is the location of many potential entrances for water into the home, the flashing is another spot that can let water in if something goes wrong. In fact, flashing is one of the things roofers need to check whenever there's a leak reported because the strips of flashing are typically put on parts of the roof that are prone to leaks, like where a chimney meets the roof. If your roof has started leaking, it's possible the flashing is to blame.
Most flashing is made of thin strips of galvanized steel, a rust-resistant metal that easily channels water down to gutters and that protects connections in roof valleys. Occasionally flashing can be made of other metals (as long as the metal is rust-resistant), but it can also be made from non-metal materials like rubber or even roofing felt. Sometimes the material used is not appropriate for the region's weather or type of roof, and the material degrades faster than expected. That could easily let water intrude into your roof and attic or crawlspace. Most homes will have metal flashing, but if you suspect yours isn't metal, ask the roofers to take a good look at it when they check for leaks.
Hail and Debris Damage
Whether it's ping-pong-ball-sized hail or a dead tree branch thrown about by a storm, anything that hits the flashing can cause damage, just as it would to your roof. While the metal flashing might not break, its edges can dislodge if the impact is forceful enough. Those damaged edges then have gaps that can let water in. And the water doesn't have to drop exactly in, with raindrops hitting the open spots perfectly; rainwater can run down the roof or side of the chimney or dormer and hit the gap that way.
It is possible, as unwelcome as this image is, for wildlife like raccoons to tear roofing materials. Not just scratch them, but tear them or lift them. If the flashing was already in questionable shape, it wouldn't take much for an enterprising animal to damage the flashing even more in an attempt to find a way into your home's attic or crawlspace. The animals just want shelter, but they can do a lot of damage when searching for an opening. They won't be able to rip metal in half, but they can lift loose corners and damage the edges of the strip.
If you're noticing leaks, you need to call a roofer immediately. The roofers will give your whole roof, including the flashing, a good inspection to find the source of the problem.