Use employee management software as the operational home for people processes when the main requirement is to manage hires, job changes, employee requests, documents, and departures—and the current enterprise system does not support that work well. An accounting record of a payee or labor cost cannot by itself coordinate those employee services.
The decision does not normally mean replacing enterprise accounting. Finance still needs its ledger, controls, and reporting. It also does not automatically require a standalone HR product: enterprise suites can include capable employee-management modules. Compare those modules and separate services against the same real employee events before deciding where the work belongs.