In large corporations, buying shares does not always lead to a stock certificate (in a case of a small number of shares purchased by a private individual, for instance).
A bearer stock certificate, as its name implies is a bearer instrument, and physical possession of the certificate entitles the holder to exercise all legal rights associated with the stock.
It's highly doubtful, for instance, that anyone buying a stock certificate for a family member is going to own another professional football franchise.