AWS documentation for "Monthly cost allocation report" says
The monthly cost allocation report lists the AWS usage for your account by product category and linked account user. The report contains the same line items as the detailed billing report (see the Cost and Usage Reports Guide) and additional columns for your tag keys.
However, I just checked my Cost and Usage Report (CUR) and it also has user-defined tags as columns.
Is the "Cost allocation report" still useful compared to Cost and Usage report? What are the features "Cost allocation report" has the CUR doesn't?
The cost allocation report allows you to view where your money is going with different metrics; the most commonly used ones include "service" & "tags". This can show a breakdown of cost by services or tags.
https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/configurecostallocreport.html
The Cost Allocation Report is just another way for people/organisations to see where their money is going and how where they might be able to reduce costs. Depending on the scale, build and type of team using the AWS account will depend what report you might decide to us.