Its already really rare for an ico to have a product that investors can test, playkey can already be tested by people who want to see the performance of game on the actual platform. Its really a good point, investors always enjoy to see that there is already something for the project and to see the project is in good way of development.
Maybe that is how crypto startups are supposed to be going public. If you look at traditional market IPOs in almost every case the business is already established before going to the stock market.
Of course it would be ideal if an ICO project already has a working platform/product, so investors have something to test and not just the idea of a team, they have to trust. But often the projects depend on the money from the ICO to develop exactly this idea they have.