Do you really want a gaming company to sell its games to an oligarch in Russia at roughly 3.7 times less the price of what they would cost in the US? Besides, it's not like a game is a vital piece of software to own. And in poorer countries, it's not like everyone owns a computer fast enough to run the latest game, or owns a computer at all.
And where it comes to non-gaming software, there are other ways a company can make sure its software goes to people who can afford it. It can create student licenses, language localized editions, versions for non-profits, nagware software, software which produces watermarked assets, web hybrid applications, open source software with various levels of support, etc. There are thousands of options, but ultimately the company making that software has to make this kind of decision for itself based on its own capabilities and based on what it thinks the market can bear.
In some countries, making payments can be so difficult as a consumer, that selling a piece of software at a fraction of the cost based on a country's gdp wouldn't necessarily work. And in other cases still, a company could easily cannibalize its own local customer base by providing competing foreign customers with cheaper software.