Why Hashtable does not allow null values?

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Tags

1. #equals
2. #hashcode
3. #these
4. #methods
5. #objects
6. #successfully
7. #hashmap
8. #allow
9. #created
10. #hashtable
11. #since
12. #later
13. #doesn
14. #store
15. #retrieve
16. #implement
17. #object
18. #method