What's this hash DB?
The insomnia hash database is a database that contains about 646 million MD5 and SHA-1 hashes and their corresponding passwords.
The hashes were generated from the combination of several large wordlists.
Welcome to 1999. What about rainbow tables?
Rainbow tables a great, no doubt. But they increase in size really fast the more characters you have in it. They can, by design, not be based on a wordlist.
A database system does not have this restriction, you can have much longer passwords too, albeit at the expense of not having the full iteration of all characters. It's also more suited for special characters. Adding passwords with special characters and characters for non-western languages is going to make a rainbow table much, MUCH bigger.
Put simply; rainbow tables are very effective for a specified set of characters and passwords up to a set length, but not (yet) viable for large character sets and long passwords.