My first thought was that most people use TikTok on mobile, whats the point of this (if the ad takes them to play store/app store or to the Uber eats app). Then I realized that this is probably aimed at tracking for new signups, they probably send them to the app stores with a redirect to their site in the middle. TikTok probably doesnt forward them the user identifier hence the tiktok pixel on their page, so they can see the effectiveness of the ad on some TikTok ads dashboard.