Why cats like to crawl into enclosed spaces:
1. When cats feel cold, they will seek out enclosed spaces to crawl into in order to keep warm.
2. When a cat first enters a new environment and feels scared, it will hide in an enclosed space to make it feel safe. 
3. When cats are anxious or irritable, they will also crawl into enclosed spaces to relieve stress.
4. When cats feel threatened or frightened, they will hide in enclosed spaces as a natural instinct for self-protection.
5. Cats are better able to hunt and catch prey when they are in enclosed spaces; this is a cat's hunting instinct.
