Is it really that easy? Lets run through this process

Step one: Find and identify a element. Then you must determine if that element can be used for anything and how you are supposed to extract it.

Step two: actually extracting it, the material could be so dense that anything short of some unknown massive force will not wrench it from its vein. Or it could be so brittle that it breaks when touched by the slightest instrument. Now what if you dont have the tools to extract it, do you engage in a possibly expensive R&D campaign to build something that can or do you just forget about it.

Step three: transportation. You will need thousands of pounds, kilos....whatever to build anything of value or to add to a stock pile, alot more then what can be carried on one ship. You will need a fleet of dedicated ships just to transport the ore from here to there, not to mention protection ( if your in a hostile sector) and you will need to account for possible losses. 

Step four: Processing. What if this new element has a high melting point? What if it doesnt have a melting point? What if it requires a sun to melt? What if it cant be shaped or refined or infused? These are all problems that can be solved by costly research of course but after everything you did to get that element here...is it really worth it. 


In reality its not that easy to find and mine materials, materials arent always on your doorstep and they arent always easy to find.