While you may find cannisters, they really have no value for explorers. Why would you take on random cargo to reduce your jump range? Why would you want cargo anyway? Sure, it may be a couple thousand credits, but if you're a thousand light years out, cargo is wasted space. All of the synthesizing materials live in the SRV, so you do not need a cargo bay for crafting materials. As a deep-space explorer, you do not need the storage space for exploration. My refit Asp has no cargo bays, but it does have a SRV and landing suite.
At the same time, I have a different ship for serious planetary stuff (Orca!), and that ship does indeed have cargo space for trinkets I find. I just don't do deep-space exploration in that ship.