Videogames, by and large, are all about acquisition, and the Ratchet & Clank games embrace this founding principle with greater fervour than most. In Ratchet & Clank, barely a second goes by without collecting something; bust open one of the series' ubiquitous crates and hundreds of bolts spill out, bust open the skull of an enemy and - like some kind of bizarre pinata.
In the case of Tools of Destruction, the more bolts you collect, the more weaponry you can buy, and the more 'raritanium' you find, the faster you can upgrade said weapons. Plus, the more you use each weapon, the quicker it levels up.
9.4 was IGN Rview score
9.2 is IGN AU review score
Thanks to MK_Red for pointing out.