There are several possible reasons why dogs like to pick up shoes:
Dogs may think shoes are toys, and they may pick them up to play with.
Dogs may like to play "fetch and loose" with their owners, so they will pick up their owners' shoes.
Dogs may pick up shoes in their mouths to attract their owners' attention.
Dogs may hold shoes in their mouths to satisfy their thirst or sense of smell.
If dogs have bad habits, they may pick shoes in their mouth to attract their owner's attention so they can be punished.
Sometimes, dogs picking up shoes may be because they are lonely or bored. If your dog often picks up shoes in its mouth, it is recommended that you try to give them more exercise and care to help them get rid of this bad habit.