According to me exchanges should promote the usage of their coins/tokens outside the exchange to build a community in support of it. If your community consists of huge individual entities who believe you then a great community can be formed. Otherwise lack of applications would lead these things to disaster.
The purpose depends on the project idea. generous payment token projects we can talk about your strategy, but for technology projects they only elaborate on blockchain technology to make the Defi system better. There are many projects with many different purposes so if only developed as you say, it is still lacking. To be clear, projects that now need to create a community with investors who trust and partner with multiple partners will increase trust for traders. That's the key to developing the token price.