@cms neuf
With a Rand you can buy coal, diamonds, and metal ore. Something, which is not exactly lacking in Russia.
With Rials you can buy oil. Again, not a good fit.
We pay the North Koreans in oil, and they're happy.
Jokes aside, there isn't enough things to buy in those parts of the world, for the amount of money that Russia was earning in excess every year.
For a good part of two decades Russia had tens of billions, and sometimes north of a $100B of excess cash coming into the country. To avoid overstrengthening the Ruble, the government tried always to remove this mass of foreign cash from the Russian market and invest it into interest yielding Western securities.
If we gave this money to the Russian people instead, by for example selling all these dollars for rubles - then we would have a Saudi Arabian style currency now that would be incredibly overvalued.
For Russia, it's actually beneficial to have a weak Ruble in the range of 60-100 rubles per US dollar. If we always sold dollars to the population, the ruble might be in the range of 40-50 right now, which would in short order bust our budget.
Russia could not make ends meet, with a Ruble at 40-50.
Why? Because we earn mostly in dollars and euros, but we owe our population in rubles (pensions, salaries, military, etc). And on the other hand, our population pays us in rubles and not dollars or euros (taxes).
So instead, over the last few years, we instead sell rubles and remove dollars from the market.