Dogs have a keen sense of smell, and they use it to gather information about the world around them. Crotches are a rich source of information for dogs.
In the animal world, sniffing is a common form of greeting. When dogs sniff each other's crotches, they are essentially exchanging information about themselves.
Dogs are attracted to pheromones, and crotches are a rich source of these chemicals. This is why dogs are often drawn to sniff crotches.
For some dogs, sniffing crotches is a calming and comforting experience. This is because the pheromones in crotches can release endorphins, which have mood-boosting effects.
Some dogs sniff crotches because they are looking for food. This is especially common in dogs that have been trained to beg for food.
Some dogs sniff crotches because they are simply seeking attention. If you give your dog attention when they sniff your crotch.
If your dog is bored, they may start to sniff crotches as a way to entertain themselves. This is common in dogs that are not getting enough exercise or mental stimulation.