The latest version of macOS (Catalina) supports all hardware manufactured since 2013 (and 2012 if you exclude the last tower-style Mac Pro and the white unibody MacBook). I kinda doubt there's a technical reason why Apple doesn't support hardware older than that, but a ~6 year support period (2013 til 2019 when Catalina was originally released) isn't entirely unreasonable.
Per Apple's specs page [0], these devices are supported.
> MacBook (Early 2015 or newer)
> MacBook Air (Mid 2012 or newer)
> MacBook Pro (Mid 2012 or newer)
> Mac mini (Late 2012 or newer)
> iMac (Late 2012 or newer)
> iMac Pro (2017)
> Mac Pro (Late 2013 or newer)
There weren't any "MacBook"s manufactured between 2013 and 2014 (inclusive). The only model year of the iMac Pro ever manufactured is 2017. All trash can Mac Pros and forward are supported, but not any of the tower style models.
Indeed, I have a MacBook 2006 that runs Windows 10 in a BootCamp installation. That's a 14 year old machine that Microsoft has been continuing to provide updates for. It's a bit embarrassing when Microsoft provides 8 years more support for an Apple device than Apple does itself.
Per Apple's specs page [0], these devices are supported.
> MacBook (Early 2015 or newer)
> MacBook Air (Mid 2012 or newer)
> MacBook Pro (Mid 2012 or newer)
> Mac mini (Late 2012 or newer)
> iMac (Late 2012 or newer)
> iMac Pro (2017)
> Mac Pro (Late 2013 or newer)
There weren't any "MacBook"s manufactured between 2013 and 2014 (inclusive). The only model year of the iMac Pro ever manufactured is 2017. All trash can Mac Pros and forward are supported, but not any of the tower style models.
[0]: https://support.apple.com/kb/SP803?locale=en_US