When reporting on operating systems market share, the news sites refer to "Windows market share", even though it is evident they discuss the installed base of the operating systems, even old versions that are not sold any more. Why they do not say "Windows use/usage share" as we do in Russian?
This is the sort of term that is idiomatic, so it will vary from language to language. We say "market share," you say "use share."
I looked up some interesting Russian idioms that have different English idioms with the same meaning.
- When a lobster whistles from the top of a mountain -- when pigs fly
- Make an elephant out of a fly -- make a mountain out of a molehill
- Warm a sheriff -- grease a palm
- Don't push the horses -- hold your horses
- If you're afraid of wolves, don't go into the woods -- if you can't stand the heat, stay out of the kitchen
- Like two drops of water -- like two peas in a pod
- If a claw is stuck, the whole bird is lost -- for want of a nail, the kingdom was lost
- When wood is chopped, chips will fly -- you can't make an omelet without breaking eggs
- Between a hammer and an anvil -- between a rock and a hard place
- Run from a wolf, run into a bear -- out of the frying pan into the fire
I'm having too much fun with this! But it shows how different groups of people find different and creative ways to express the same ideas.
I found most of these here, in case you're interested in seeing more of them.
Two things here.
First, I'm not sure your statement that discussions of market share are referring to old systems not in use any more is totally accurate. For example, Microsoft/Windows' market share may include millions of Windows 7 PCs even though we're on Windows 10 now because there are lots of people and especially businesses out there that aren't on the latest version of the OS. And as long as those people/companies keep running an older version of Windows instead of buying a Mac or Chromebook or whatever else, they're still contributing to Microsoft's share of the computer market in the broader picture.
But second and more importantly, as Investopedia explains, market share generally refers to a dollar amount, not a number of units. So let's say the whole world computer market is only five computers. Of those five, four are Windows computers, which Microsoft sold for 100 bucks each ($400 total). The fifth is a Mac, which Apple sold for 400 bucks. If that's the case, Microsoft and Apple each have a 50% market share in the computer market, even though the number of Windows computers comprise 80% of the market by units.
If we were to say "use share" or "usage share," that could imply we are talking about the number of units in use across the market – the 80% figure in the example above – when in fact we are referring to each company's financial footprint in the market – the 50% figure in the example above.