Common stock is also shielded against liabilities, as in it can go to zero, but can't go negative. Equity can.
Common stocks are really strange, they are much closer to tokens, than to actual pieces of the company.
But to your point about common stock, even when a publicly traded company undergoes a buy-out, they will require their purchaser to pay a premium on their current stock price ('current' typically meaning average over the last few months). As an example, if they are currently trading at $20 per share, they will require the purchaser to pay $30 per share to acquire. Once this is announced the common stock price will jump to the buyout price; at which point major investors of even common stock get a significant return. The reason for the jump is because the purchasing company will either payout cash or the stock will convert into the new parent company's stock. On the other hand, who knows what happens with tokens upon acquisition; there is no legal obligation whatsoever.