Do visitors have questions about your product after reading your sales page? Identify areas for further explanation, and increase your conversion rates.
Does a visitor love your product, but wish it had a built-in chat feature? Identify features and benefits important to your customers by asking for feedback.
You've already sold visitors who signup. What's important is understanding why visitors don't signup. Analytics can identify bounce rates, but why does a visitor spend 60 seconds on your site then leave? Identify their objections, then fix it.