Microsoft has been constantly upgrading Skype and it also means taking some hard decisions. Microsoft has stopped providing support for Skype for many older versions of Windows. For example, Skype is supported only on those phones that have received the Windows 10 Anniversary Update. If your Windows phone hasn’t received the latest update, you won’t get any support for Skype. This doesn’t mean you cannot run Skype on your phone running an older version of Windows, it’s just that support is not available. If you have some problem running Skype on an older version of Windows, your problem won’t be solved and you will be asked to upgrade to the latest Windows 10 operating system, or forget about using Skype.
It also means that right now you can directly download Skype on your mobile phone unless you are running the Windows 10 Anniversary Update. There is a direct link, though. But even this direct link won’t be able to work after some time.