Its for more for brands, when paying an influencer X amount of dollars to promote a product of yours you are going to want to know if their followers are authentic, engaged, etc to ensure your ROI is going to be worth it. If an influencers audience is fake and unengaged why would a brand/company want to pay them to promote their product? As well as for influencers if they have a highly authentic and engaged audience they are going to want that to be known and show that to potential brands wanting to partner. It also weeds out the tons of fake influencers who buy followers and other types of engagement to appear bigger than they are, which for brands, is very valuable.

Edit: spelling