Most of the time (if not all the time) we are obsessed and observe the traffic and engagement metrics. Because that’s what we like to see and that’s the result we want. If your an influencer or media, sure. 

But as a business, the number of followers, how many likes, views, or comments; does not equal sales. Views and comments do not pay the rent or profit for the month. But it does bring up your brand. 

So, when your planning your Marketing Strategy or Campaign, decide what result do you want; let everyone know including the marketing agency. 
A marketing agency or a marketing individual by default does Brand Marketing that can generate views, comments, or followers. That’s the easy part (technically). The hard part is converting these numbers to a sales result or growth. 

What you can do is a 10:1 ratio. For every 10 posts on Social Media that bring up your brand, post 1 for Sales (promotion, product launch, .etc). 

Social Media for Business is really complicated, to be honest, the strategies you put in place might be a hit or miss. The only way to see a sales result is to create 1 strategy at a time and just launch it till it’s complete and see the results.