tanach - Why do Sifrei Emes use different taamim?

I know that the Sifrei Emes (Tehillim, Mishlei, Iyov) use a different system of taamim. Why is this?

What is it about these books that makes it that they cannot — or should not — use the regular system? (Or, for that matter, what is it about all the rest of the books in Tanach that makes them unable to use the taamei emes?)

Answer

All three books (Iyov Mishlei and Tehillim) are written in a complex poetic style. The separate trop represents the shift from prose to poetry and may have been sung in a more songful manner than the regular prose trop. A proof to this distinction lies in Iyov, whose first, second and final chapters are written in prose and have regular trop.

EDIT: The structural difference between the prose and poetry parts of Iyov can be seen in this clip from the Aleppo Codex (Keter Aram Tzova) showing Iyov 2:11 - 3:6. Notice how once it switches to poetry, the text is split into two columns reminicesnt of the way Ha'azinu is written in a Torah. This pattern extends through the poetic sections.