Steam just makes sense as a fluid for heat engines, thermal power plants are mostly steam, except when gas turbines are involved, but even then there's most of the time steam bottoming cycle. (gas turbine burns something, then exhaust is hot enough to power steam cycle) Unless thermal power plant is small, then it's more likely to be diesel engine (up to few MW). Only when it's photovoltaics, or hydropower, or wind farm (or tidal powerplant, or some other weird ones) there's no place for steam to be involved (solar thermal plants sometimes use steam cycle). Geothermal powerplants use steam if source is hot enough, otherwise it's something more volatile in organic Rankine cycle
Then it's just heat transfer medium for most of geothermal powerplants too, because from what i understand, most of the time condensed water is recycled (and source of energy is just "hot rocks" anyway)
then if you look at the bigger picture, all that energy can be traced back to either sun, nuclear fission (in reactors) or nuclear decay/primordial heat (geothermal)
Then why focus on steam specifically, why not other required intermediaries, like turbines, the storage mechanism.
The main meaningful distinction in energy generation is the root sources of the energy, nuclear, wind, hydro, etc. All of those share similar conversion methods and intermediary forms, but have different sources.
Arguably these are even greener than photovoltaics, since they don't require the same kinds of materials to make (mostly just steel) and last longer than photovoltaics are supposed to. They use a fair bit of water, but you probably aren't building them in places where water is at a premium.
I mean the main steam cycle solar plants are built in dry sunny hot regions, not exactly a great source of water, but probably not completely void of it either.