The act of turning AIS off can attract unwanted attention (higher resolution local satellite monitoring), less likely if you are entering waters where piracy is common and many vessels disable AIS.

If a vessel turns AIS off then cuts the cable, but their position is known by other means, they will be giving up plausible deniability.

Every ship in the Baltic sea is monitored and accounted for at all times, if your beacon suddenly disappears you're practically screaming look at me.