This is mostly true, but a number of tokens actually do generate an income in the form of fees, inflation rewards, or a combination of the 2. For example, ETH can earn staking rewards, and post ETH2 merge, will also earn transaction fee revenue. A number of the dexes generate trading fees that get distributed to token holders (giving P/E ratios that are high, but not absolute insanity given they are "growth" stocks).