Investors need attention, but listing is not the only way to do this. There are many different ways.
Every project needs promotion and development. It is necessary constantly to develop and becomes better. Usually investors carefully check how actively develops the project and how active the team.
Of course, it makes no sense to invest in a project that stands still. I like that the project has found a non-standard approach in development, it offers something new to users.
It is very hard on the first stage of development and on the stage of IEO to understand how project will develop in future. Very often after the end of IEO projects stop to develop.