In general, the categorization of requests is helpful when you deal with large projects.
Analyzing customer needs and identification of the correlation between the subject of the request and your work: For example, after each advertising campaign, we are asked more questions about pricing; that means that we need to provide links and include information directly into the special pricing offer description. If you are frequently asked questions starting with "How to…?", make sure you have the answers to the most commonly asked questions publicly available in your knowledge base section. If the number of the "returning" customers during the month was more than usual, then you should ask yourself - what went wrong with the customers' communications?
Filtering requests: This is straightforward. Categories let you set the filters and avoid confusion. For example, you can categorize the requests not only by a type of question but also by the team that should handle the request ("Sales", "Support", "Marketing", and so on). By doing so, you can flexibly configure the filters and not get lost in the requests addressed to other teams.
Automation and optimization: For example, all tickets in "Return" category should be immediately assigned to a particular agent or to a group of agents from the Sales department. If you notice the question is frequently asked, then, to optimize the workload of the customer support team, it is a good idea to create an answer template, or set up an auto-reply. The lower the agents' total workload, the more time and effort they can devote to each client individually.