While a CNAME implementation does not provide any benefits in terms of cookie lifetime, there may be some other benefits. These benefits include ad blockers and less-common browsers preventing data from being sent to domains they classify as trackers. In these cases, using a CNAME can prevent your data collection from being disrupted for users employing these tools.
In addition, CNAME implementations allow you to specify Choose custom RDC type which controls where users’ hits are initially routed. The majority of customers do not use custom RDC types.