If you can measure it, you can improve it. This saying is always applicable in outreach. After you sent out messages to your target linkers, you have to track the response rate and the number of links you acquired from them for the following reasons:

• You can have a better understanding on which template gets the most response and certainly add/change details to the template to get better results.
• You can estimate your industry's link acquisition rate for a certain portion of contacts (2% rate for the first 10% of the whole list).
• You can determine which day of the week yields the highest results in outreach.

There are still a lot more reasons why you need reporting in link building outreach. But the above reasons are what you need the most to improve your outreach efforts.