With the best I know, native tokens are designed for users to gain accesses in the coins blockchain it's also for incentives purposes by which the coin network could extract transaction fee while user are in used of the network.
During a network project, it can also be be used to reward participants of the projects.
If thinking the need of developing native tokens are unnecessary, then we should have rethinks about the need for the development of AltCoins after Bitcoin was developed since they're all cryptocurrencies alternatively serving same purposes in the economy and financial system.