Discrimination is easier to achieve with fuses than circuit breakers especially in small sizes. At a small installation you can get three layers of discrimination with 50A, 32A and 16A fuses or even 40A, 25A , 10A. You can’t do this with breakers. Often these installations have a fairly small diesel generator and the top level of protection should be kept small enough to be cleared by the available current from the alternator. If there is a UPS, that complicates matters further. Fuses are often the only option to ensure a short circuit in a sub-circuit does not take out theb whole site (it has happened)