This is tied to the the root motivation in YC: do good for society by enabling more startups to exist. That's is a side effect not directly tied to investments

This is tied to the the root motivation in YC: do good for society by enabling more startups to exist. That's is a side effect not directly tied to investments in YC companies, as new angels will certainly also invest elsewhere. This isn't to say you're wrong. More investors in YC companies is a direct motivation for the conference.