Firstly, all Ethereum blockchain transactions are not free-of-charge. Without commission project will lose money and be unprofitable. In addition, its a must to pay for marketing, office expenses and other. Sure, it is possible to create a project which will change the world, but its impossible to without proper work conditions. Thus, every project should be profitable and take money for any kind of service.
It becomes profitable due to token capitalisation! The more popular the project is, the more expensive its token becomes! Simple