I imagine that commercial power rates are less variable than residential rates. Nonetheless, providing fixed-cost charging, could get complicated across different states/regions/timezones.
Capital costs are currently sufficiently higher than charging costs that strategically over-provisioning yourself with fleet in order to reduce your average charging cost is not worth the money.
Besides more exposure to wholesale fluctuations and time-of-use, there's also things like demand charges, where there's a price component based on your maximum power draw rather than your consumption -- max kW in addition to sum kWh.
Demand charge management is a lot of what these commercial charging platforms do. It's fine when a single fleet vehicle comes up to charge, but when a couple show up to charge at the same time all with different times-to-departure, that's when you need to do some selective prioritization and optimization to not get ratcheted to your highest kW demand charge for the month.
Then, if you run any industrial-grade machines (or even elevator motors), that's when they start adding additional charges for things like uncorrected power factors -- https://en.wikipedia.org/wiki/Power_factor
[1]: All these things are coming to resi, though... time-of-use rates are increasingly common (it's now the default new rate in CA), and two or three states are experimenting with resi demand charges.