Dictionaries are not like Websters. They include several categories such as default passwords (admin), most-used passwords (abc123), and such. Plus, attackers will also use proper names and common words, with numerical substitutions for letters (G00gl3). And if they are really after your use of a particular website (like a bank) they will try to change a password there to learn the parameters of that site (like passwords must be 15 characters long, or that they must start with a capital letter, or that they must start with a numeral, or include symbols).
This is called reducing the search space.
And yes, it results in more possibly-valid keys being searched per unit time as opposed to using raw brute-force)
Then they will do things like call tech support and provide answers to the secret questions (what high school did you go to, mother's maiden name) or anything they know (and for public figures a lot of that gets published). This is how Kevin Mitnick did most of his cracking.
Brute-forcing will always work, given enough time, but generally there is no need for it.
So even though your processor will not actually search any faster, it will definitely search faster through relevant possibilities with the use of dictionaries.