The focus on cin / cout as opposed to GUI is probably because cin is simple and always works the same way (mostly because nobody uses it, no need for a zillion libraries), whereas there are a lot of very different GUI libraries with different ways of doing things; learning one of those would take time and not help you use another one much.

If you want to learn yow to make a GUI you can probably find a "hello world" example for your language/os of choice and just copy-paste the code and then adjust it to suit your needs.