Lots of reasons. You need energy to store the information. You wouldn't be gaining anything, only losing efficiency. The quantum level is the "lowest" level of existence, there's nothing "lower" to use to simulate it. Furthermore, "random" is a critical concept in QM, and one can never achieve true random with a TM. What's the digital algorithm to generate a truly random number?
Edit: in a way simulating a crab with a bunch of crabs would be kind of like simulating energy dynamics/QM with energy
Edit: in a way simulating a crab with a bunch of crabs would be kind of like simulating energy dynamics/QM with energy