"The Windows API is designed for C and doesn't fit will into C++'s methodologies. Not only that, it limits you to Windows. I personally have not used MFC or .NET - if I ever need to develop something that will only run on Windows,"
I did research and MFC is more like C++ because it's is a library that wraps portions of the Windows API in C++ classes, to make it less C-like.
Why would you use QT if 80% of laptops/desktops use Windows? Android and IOS are the second most popular OSs, so why not learn their native APIs?
Because people still use those non-Windows desktop/laptop platforms for a myriad of reasons. Developing for them is a courtesy that is slowly becoming expected. Additionally, not only is Qt cross platform, but it's (IMO) vastly better designed than Microsoft's APIs.
And don't forget that it takes time to become familiar with each large API that you learn. It's faster and cleaner to learn Qt than to learn three native APIs that all do things in different ways.
Sure, there are disadvantages to doing things that way. But for a beginner, I'd be inclined to recommend Qt over native APIs, because the latter gives them ties to a platform early on.