It's another part of the software lifecycle
Various types of user research can be used throughout the software lifecycle to address various challenges. For example, user stories can help to prioritize features requests. Usability testing can help refine future designs. Etc.
Benefits of user-friendly software: Studies have shown a wide variety of benefits when usability is included in the product cycle, e.g., lowered development costs, increased sales, and reduced support costs. User research can directly impact end users’ effectiveness with the product – a quantify-able property that can be used in marketing.