The listing of tokens on exchange does not guaranty the investors that price for the tokens would grow. People must use the tokens that their price would grow.
That's true, but at least listing is the first stage for the coin to get recognize and to satisfy the investors that the team are doing their job to provide liquidity on the coin. When it's on the exchange, they can continue developing the project and if they do a great job, demand will be created and it will be easy for investors and traders to buy since it's already accessible in the trading site/s.
Very often happens when after the listing start airdrop members and bounty hunters start to sell tokens and their price falls. Investors lose trust and sell the tokens too.