Some companies experience liquidity events. Therefor the value of equity in those companies is positive. Some companies go out of business. Therefor the value of equity in those companies is zero.
If N is the ante hoc chance that a company will experience a liquidity event, then:
N * X + (1 - N) * 0 = value of liquidity
X is positive. 0 < N < 1.
Therefor the value is positive.