Dislikes were a fantastic way to determine if a video had a misleading thumbnail or title at a glance. Now you have to waste time determining if the contents of the video are factual or not, which can become infuriating, especially for technical work that demands accurate information.
They exist on fewer servers, so they have to be pulled from deeper levels of cache, or maybe even no cache. Popular videos will be cached on edge servers all over the place, and will be quick and easy to deliver.