RPA's are used to simplify the work for the End users. Think there is an application which is in traditional Mainframe which the team is not refusing to upgrading citing the absense of business knowledge or do not want to rewrite the complex business knowledge. Such apps would be tougher to use for the newer users. RPA's solves this issue by scraping the data from the screen and fill in to the required forms.
When 2 applications cannot be interacted to derive results and feed into 3rd application, then RPA can solve the issue. It will open the apps, read the data and feed the data into the 3rd app.Such sceario RPA can work in a single click. All tedious, repetitive jobs can be automated.