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.
But in my view, at least these exchange tokens are having one real-world application unlike most other crypto coins and tokens because most of the crypto coins and token are just being created only for speculative reasons but exchange tokens are created for providing discounts on exchange fees.