It is the cheapest and most feasible way to monitor fetal well-being during labor. But that is costly and rarely possible. Studies also show that electronic fetal monitoring is associated with reduced neonatal seizure rates and lower perinatal mortality from hypoxia. Anecdotally, fetal monitoring also saves lives. It can detect a heartbeat that suddenly drops to levels that require an immediate lifesaving cesarean.
Intermittent auscultation misses that.
Anecdotes don't impress epidemiologists, but they've convinced doctors and nurses on the firing line that fetal monitoring is useful. Most of the studies that show continuous monitoring no more beneficial than intermittent auscultation are flawed. And interpretation of fetal monitoring was inconsistent. Unfortunately, doctors don't interpret fetal-monitor strips consistently. What is fetal distress to one doctor is not to the next.