To be fair to Microsoft, the world keeps moving. Just as Outlook Express became dated and was replaced by Windows Live Mail, it probably made more sense for the free e-mail program to become a Windows Store application. Mail and Calendar on Windows 10 (and possibly Windows 8.1 - I never used Windows 8 or 8.1) is functional but basic.
If you want a 'full feature' offering, there is Microsoft Outlook 2016 - at a cost, of course. It's not perfect, especially when used as an IMAP client, but it works. There are free alternatives, such as Thunderbird. It's probably time for Windows Live Mail to disappear. It doesn't work with outlook.com any more, it hasn't received any attention for many years, and there are better free alternatives.
There has been an industry-wide move to more aggressive deprecation of old, end of life, software - something that has particularly concerned Microsoft, with the high number of Windows XP installations still in active use at the end of life date. Microsoft is now much more prominent about product lifecycles and typically removes downloads for end of life products on the EoL date. Microsoft have also taken to archiving support content for end of life versions is archived.
So many security issues arise through old technologies and implementations. Thankfully the industry has moved on from not deprecating anything for fear of the resulting compatibility issues. I'm waiting for the day when I can remove Flash Player from my machines and feel secure in not breaking any web sites.