Aluminium is still valuable today because it is so practical for things. Scientists and engineers have gotten adept at changing the metal around and fashioning it for practical use. We use aluminium in many things on a daily basis. For this reason, it is still a valuable metal because it has so many diverse uses in every day life.
Aluminum is one of the most plentiful substances on Earth—the most common metal found in the planet's crust. But aluminum is also a friendly element, and it's often found bound tightly to other elements. (Some jewels, like rubies and sapphires, are made mostly of aluminum oxides.) It wasn't until 1825 that anyone was able to produce even a sample of aluminum, and even that wasn't pure. So despite being incredibly plentiful, aluminum was also very rare, and therefore valued: Napoleon honored guests by setting their table places with aluminum silverware, even over gold. The Washington Monument's six-pound aluminum cap was an extravagant embellishment.
The way that we now use aluminium is different than how it was used before. For example, we use it in the form of foil in order to wrap food. It is valuable as far as usage but is not valuable as far as price. The cost for aluminium in any form is fairly cheap.
Once upon a time the world was filled with aluminum foil and aluminum-based deodorant. Now, however, the material's time is up and people are recognizing the health risks associated with using aluminum too heavily (if at all). This means that aluminum is not nearly as valuable as it used to be.