Let's be honest here. For years the cruiselines have surveyed cruisers on embarkation asking if they had any symptoms prior to boarding, ie, have you had fever, sore throat, etc.
I am surmising that some of the more fervent Covid testing advocates have at one time or another not acknowledged a 'symptom' so their cruise was not impacted.
We are excited about the return to more common sense restrictions but realistically do not think many will bother to test without symptoms and no need for test verification. JMHO