BI tools is often used for analysis of ERP data on aggregated level. Analysing e.g. production, sale or finance data, you might come to a point where not all details are available through the BI tool.
For these cases, users would sometimes value a 'drill-into' the GUI of the ERP system, e.g. marking an order number and jumping directly to that order in the ERP GUI. same possible for cost centers, customers, material or anything.