Does fundraising really validate your startup?

A funding announcement can make a company look successful, but it does not prove that customers want the product or that the business can sustain itself.

The more durable signal is often simpler: you ship something useful, generate revenue, and use the profit from product one to fund product two. Each product becomes evidence that the next one can exist without another raise.

What would change if founders treated revenue, rather than fundraising, as the main validation milestone?