For a long time, there is a doubt among lots of Windows users especially those English speaking users, that is why Microsoft chooses Alt+F4 to close a window instead of Alt+Q. Alt+Q is more comfortable to press for many keyboards, also Q represents Quit and it is easier for people to understand. Recently Microsoft answered this doubt.
Raymond Chen, longtime Microsoft developer and semi-official Windows historian, said the reason is that not everyone speaks English. It doesn't work that way in many other languages. You have to choose a common key sequence which people from different places can use, it doesn't need to be localized.
In addition, different keyboards have different layout because layouts can be customized. For example, if you are in France, the letter Q is not even at the upper left corner of the keyboard. So if you choose Alt+Q as the hot key, you still need to find the letter Q. Hence Alt+F4 is a kind of safe combination because the Function key isn't going anywhere and it's rarely customized. You can find it even if you are using different keyboards.
