Well, how does it not necessary for a team to prove the viability of their project? If investors do not see prospects, they will not buy tokens of the new project.
Do not you know how many scammers in the environment of crypto startups?
Everything is so, because this is enough to present an idea, a site, a roadmap, white paper, a team. Nothing more. Enough to promise. There is no evidence, since it is impossible to prove the viability of what is not yet working.
If you come to an investment fund with this, you are unlikely to be given money to develop your idea.
That is why it is important to check not only idea of startup but its ready products and development.