For the original poster, because they might be used to running primarily a distribution-installed version of emacs: the code for unix-based GUIs has supported a variety of these sorts of elements for a very long time, depending (currently) on whether you build emacs with the Athena, Lucid, Motif, Athena3D, or gtk[,2,3] toolkits. Under macOS, one has the ns and mac ports, and under MS Windows, it uses the local gui toolkit (which I believe is the core W32 look and feel, not the frequently-shifting WPF, Windows Forms, Metro, UWP, etc. standards). Even within these systems, there are options inside emacs for giving buttons a 3D look or not, and there are many packages that add icons to emacs' display (via fonts, as far as I can tell) that can 'spiffy up' emacs considerably.
It would probably be helpful for emacs' adoption if some of these gui enhancements could be added to emacs and/or ELPA more directly. To be specific, it would perhaps be helpful for emacs new-user adoption if people didn't feel the need to adopt a large integrated package like Spacemacs or DOOM emacs just to get graphical niceties -- not because those bundles are bad, but because they add a *lot* more than just the gui enhancements. The past couple years has seen a bit of an explosion of packages like better-defaults or "starter kits" that aim to improve the new-user experience without such a large overhead, but those still require getting emacs from somewhere other than GNU or the standard distrubutions, which is an extra hurdle.
I would be happy to help with such an effort, but I'm unsure what sorts of changes would be acceptible to "core emacs", and I don't personally have anything major to add to the existing set of third-party starter kits or mega-bundles. If someone here had a clearer idea, that would be helpful. Maybe the first step is to try to get all-the-icons (
https://github.com/domtronn/all-the-icons.el) or an analogous package included in emacs?
Hope that helps! Thanks,
~Chad