come on get a little bit closer baby, cause tonight is the night
A cookie may have multiple users associated with it. It seems to be a common choice to use the "last_value". But why? Wouldn't it be better to use the first user ID, that way you guarantee that your mapping/stitching table never changes. As a consequence, downstream metrics will not jump around if a 2nd, 3rd, ... user gets associated with the same cookie.
 Snowplow does the same: https://github.com/dbt-labs/snowplow/blob/main/models/identification/default/snowplow_id_map.sql