However, the situation is a bit better than this as a practical matter.
For example, the inherent thermal noise creates a noise floor of -120dB; that is, of 20 bits. Thus in a 24-bit system there already is 4 bits which can be thrown away with no loss of fidelity through 24 dB of attenuation. It is not bit perfect, but there is no practical impact.
Additionally, no recording possesses a dynamic range of 120dB. Consider a pop concert. The sound level can easily reach 110dB peak, but will will not go below 60dB (the level of a conversation in a quiet room). This is a dynamic range of only 50dB, easily captured by 9 bits. One actually needs a few more bits for convincing fidelity, .but this illustrates the concept.
All digital volume controls through away bits to attenuate volume. This is how they work. However, a sophisticated 32-bit volume control can decrease the volume of even a 24-bit input by a minimum of 12 bits (72 dB) without even a theoretical quality loss - more as a practical matter. (The DX50 has a 24-bit chip).
So there's no point in playing 24 bit files, since they will drop out.