This is something that comes up a lot in demos and I think there are three good reasons to do Ideal Customer Profiles (ICPs) with your clients instead of just for your clients:
ICPs are inherently beneficial. (Yes, I'm clearly biased, but see if you agree with the paragraph below.)
Creating ICPs with your clients means more billable hours.
Creating ICPs with your clients is a good way to include them in the process without having them get in the way. (I say this as an ex-creative who HATED having clients in the room when ideas were getting kicked around.)
So... the benefits.
Creating and using ICPs is a great way to get everyone internally and externally on the same page, talking about the same things, and moving in the same direction.
To put that in presentation speak:
It really is kind of amazing how many problems can be solved, circumvented or avoided altogether just by having the "single source of truth" that well-crafted ICPs provide.
The second benefit it is billings and you can do the math yourself: say, 5 to 7 people x 2 to 4 hours for an ICP workshop x everybody's individual hourly rate = $$$
True, you'll get that whether you create ICPs with your clients or for your clients, but doing it with sets you up for the third benefit: bonding and buy in.
When your clients directly participate in the process, they own the output.
They get why it is the way it is because they saw what it took to create, so it becomes a touchstone/filter for whatever you present and propose down the line.
And unlike, say, having them join in on brainstorming sessions for creative, positioning, strategy, etc., the dynamic in an ICP workshop isn't as fragile and can't be "thrown off" as easily by somebody who's judgmental, closed-minded, competitive, mean, etc.
Here's an example of a B2B ICP:
Here's an example of what we call a "functional module" that provides more pointed insights in marketing:
Here's an example of the sales insights:
Here's an example of UIUX insights: