Edit:

Sort of, but not in the way you are thinking about it.

People want help with this yes, but they shouldn't be outsourcing it.

The founder needs to ask literally thousands of questions to the market (can vary depending on how simple or complex the market is). If they haven't asked these questions, then they shouldn't be outsourcing it.

If they have asked all the questions, they know who to approach, what to say, how to say it. Then they can hire consultants to help them build the sale engine, which is actually all about adopting the best tools, distributing work, hiring, performance management, incentive structure, etc.

The parts that are specific to the startup (who to connect with, what to ask, what to say) need to be figured out by the startup and done by the founders. The parts that are more generic to all companies (hiring, training, performance management, team structure, tool stacking). Can be outsourced, and probably should be if the founders don't know how to do these things or really don't want to.

Edit 2:

The reason the founders shouldn't be outsourcing this, is that the founders are the ones to decide which part of the market to focus on and what to prioritize in the product. If they try and outsource it to someone else, there is an extra layer of noise in the communication between the two.

There is also this thing called the innovators bias (lots of cognitive biases really) that will exacerbate the situation because the founders with the power will over-weight their own incorrect instincts against what they hear from one person (consultant), but they will more appropriate weight their instincts against what they hear from dozens to hundreds of actual possible customers.