The shielding layer will also couple electromagnetic noise. For example, the pulse signal on the cable will form a loop current on the shielding layer without grounding, which will lead to the potential difference at different points of the shielding layer and cause noise propagation. For example, external electromagnetic waves will propagate on the shielding layer without grounding (just like an antenna). Therefore, the shielding layer generally requires grounding.
The purpose of grounding is to make the signal induced by the shielding layer have a low impedance channel. Because the impedance of the ground signal is relatively low, everyone likes grounding. Commonly used grounding points are equipment cabinet, laboratory ground wire, and home 220v protection ground (this ground will be connected to the building). If it is "gone with the wind", the effect is not good.