They also have the benefit of being more reliable, less complex and requiring much less maintenance.
A simple analogy would be a car that had to be serviced and pulled apart every couple of thousand miles, compared with one that only required a service every 18,000 miles or once a year.
Make that a commercial vehicle, a delivery truck for example, and that difference has serious financial consequencies. No company would want its trucks in the workshop all the time, costing money and losing revenue.
Think of freight locos as delivery trucks and you can see why a loco that costs more time and money to keep running is a liability.