What is so special about oysters?

"Oysters" by Edouard Manet, 1862

 Shall the world, then, be overrun by oysters?

What? Apart from this?

Sarah Waters in Tipping the Velvet (1998) tells us more:

I opened no more shells for Kitty, for she managed them herself. 'Look at this one!' she said, when she had handled half-a-dozen or so. 'What a brute he is!' Then she looked more closely at it. 'Is it a he? I suppose they all must be, since they all have beards?'

Father shook his head, chewing. 'Not at all, Miss Butler, not at all. Don't let the beards mislead you. For the oyster, you see, is what might call a real queer fish -- now a he, now a she, as quite takes its fancy. A regular morphodite, in fact! (p. 49)

I love oysters.