ZFR: It's completely normal that when value of currency A falls in relation to currency B, then people from country A can buy less products. Why should it be any different with games?
Because it's one-off digital goods.
If you make physical goods like cars, you got to pay for labor and materials for every single unit you produce and it will be priced according to the cost at the source. For example, if it's made in England and if the cost of labor in England happens to be higher relative to other places because their currency is strong, it will be more expensive for those with weaker currency.
With non-service oriented digital goods, the first copy you come up with is extremely expensive to make. The remainder are the price of bandwidth.
Ideally, you want to adjust the price of one-off digital goods to what your customers can pay (not as an absolute price, but as a relative price depending on how much people are making where each of your would-be customers live), because you want as many people are possible to afford your product: the cost factor is negligible and each sale is almost pure profit.
To a certain extent, they do that during temporary time windows with heavily discounted sales on digital games. In some areas, they won't be able to afford the games at full price, but once it's 90% off...