125 seems low but if they get decent usage off peak and from hockey or charge a lot maybe they can make money. It's lovely to skate on empty rinks, not so lovely when the rink closes because it is making a loss.
In the US, the economic viability of most private rinks depends almost entirely on hockey [for this discussion, I'm excluding elite figure skating training facilities and rinks subsidized by tax dollars]. Crowded public sessions (e.g., weekends, holidays) make money. But light public sessions (e.g, weekday mornings) do not. However, the incremental costs of running a light public session vs not running any session at all are not all that high: e.g., there is still the high cost of keeping the ice frozen, whether it's used or not. That is, some rinks here will schedule a public session if there is otherwise no demand for that time slot.
The question then is whether extra staff is needed for a public session. At my home rink, during anticipated busy sessions, there are: a person for the skate rental counter and a guard [what you call a steward] on the ice. But during anticipated light sessions, there aren't: the person at the front office also handles the rentals if needed, and there is no guard on the ice. The Zamboni driver is on duty and paid regardless: if there is a public session, he spends 10 - 15 minutes doing a cut; otherwise he works on other tasks. At one rink, during light sessions, one person cut the ice, handled payments for admission, and handed out rentals. At another rink, one of the office workers pauses her clerical tasks and serves as a guard [here it's common for skaters to work part time at a rink, because they get free ice time].
Another reason for maintaining public sessions even if they do not make money
per se is that they serve as a feeder to programs that do make money. Typically you first try out skating during public sessions. Then, if you decide you like it and wish to pursue it further, you sign up for group lessons, private lessons, hockey programs, figure skating programs, .... And there's a much higher probability that you will like it if you are sharing the ice with 10 or so other skaters than 100 or so other skaters.