You don't generally build a large supercomputer to simply run a task faster than on a smaller cluster. The goal is to enable more realistic simulations by solvi

You don't generally build a large supercomputer to simply run a task faster than on a smaller cluster. The goal is to enable more realistic simulations by solving problems using a greater number of unknowns, increasing the fidelity of output. So no, these machines are often used for problems which really do utilize the large-scale nature of the computers.