Long wires are real macroscopic bodies, kilometers of superconducting wires are used at the LHC of CERN and the currents can be described by quantum mechanical equations.
Crystals also can be described by quantum mechanical equations, and can be quite large, maybe not as large as a table. Superfluids too are in the realm of macroscopic quantum mechanics.
The difference with a random object, like a table, is that the individual wave functions of the microcosm of molecules and atoms that compose them are incoherent with each other. Coherence means that all the phases of the probability wave functions of the ~10^23 molecules per mole composing them are lost statistically, in contrast with the examples of coherence above. That is why we use the density matrix to describe the behavior of such systems.
So the random bodies that surround us cannot be described by one wave function in the sense of a solution of one quantum mechanical equation, except when careful conditions are met as in the examples above.
Edit in response to comment:
"Coherence means that all ... " Could you please elaborate more on this, maybe with the help of math?
Any wave solution will have a constant angle phi as a phase with another wave solution.
These phases are what define interference and beat patterns in waves.Coherence means that the phases are known.
The square of the quantum mechanical wave solution is the probability to find the particle at that (x,y,z,t) and the interferences patterns when the phases are fixed are also probability functions.
And you say that superconducting wires are described by usual QM,
Not usual QM, it is a special solution within the quantum mechanical theory, from the link:
Since the discovery of superconductivity, great efforts have been devoted to finding out how and why it works. During the 1950s, theoretical condensed matter physicists arrived at a solid understanding of "conventional" superconductivity, through a pair of remarkable and important theories: the phenomenological Ginzburg-Landau theory (1950) and the microscopic BCS theory (1957). Generalizations of these theories form the basis for understanding the closely related phenomenon of superfluidity, because they fall into the Lambda transition universality class, but the extent to which similar generalizations can be applied to unconventional superconductors as well is still controversial. The four-dimensional extension of the Ginzburg-Landau theory, the Coleman-Weinberg model, is important in quantum field theory and cosmology. Superfluidity of helium and superconductivity both are macroscopic quantum phenomena.
and the link has further references.
hence their wave functions belongs to a kind of tensor product of state spaces of constituting free atoms.
If you read up on superconductivity you will see that it is not what you assume.
from the link:
The theory describes superconductivity as a microscopic effect caused by a condensation of Cooper pairs into a boson-like state. The theory is also used in nuclear physics to describe the pairing interaction between nucleons in an atomic nucleus.
But what happens when the temperature rises?
the cooper pairs break up with higher temperatures and incoherence reigns.