Ships cost an incredible amount of money, against expensive jet powered shaheds traditional AA MANPADS like Stingers are absolutely cost efficient. Cheaper propeller shaheds like the ones russia used to be able to field effectively (and Ukraine has free reign to use anywhere in russia) on the other hand are not efficient to shoot down with traditional MANPADS (which is where layered air defense comes in).
Large slow moving ships in the open ocean is the easiest thing to see.
Ships cost an incredible amount of money, against expensive jet powered shaheds traditional AA MANPADS like Stingers are absolutely cost efficient. Cheaper propeller shaheds like the ones russia used to be able to field effectively (and Ukraine has free reign to use anywhere in russia) on the other hand are not efficient to shoot down with traditional MANPADS (which is where layered air defense comes in).