Direct traffic is often mislabelled traffic: someone tapped a link in an email app, a bio or a podcast description that didn't pass a referrer. Without tagging, those visits and the sales after them get credited to nothing.
Create a short link per placement in Settings → Tracking links with the destination and UTMs to apply. Presets for newsletter, SMS, Instagram bio, YouTube and podcast or QR fill them in. Each click is counted and redirected to the destination with the link's UTMs and source tag added, and tracko.js picks them up like any tagged ad click.