I'm asked this question all the time.
In my experience, the benefit to creating and using Ideal Customer Profiles (ICPs) is that they get everyone on your team on the same page, moving in the same direction, using the same "single source of truth" instead of being all over the place.
In other words, ICPs provide:
1. Focus
2. Alignment
3. Direction
If you've ever worked with (or for) an organization that's out-of-sync, you understand how big a deal that is.
Here's an example of an ICP for a fashion designer:
