No, but, sadly it is far from unknown. Several elderly people I have known were convinced that small sums were disappearing and, being far from doolally, took evasive action (sat on cash etc. when cleaners/carers in) ..... the disappearances stopped.
People in low paid jobs can be as poor as those on benefits but even some wealthy people steal when they have the opportunity. Some folk are desperate but I expect most are just greedy.
Sadly there has been several reports over recent years of carers caught on webcams stealing from their clients.