Font Awesome just updated to 5

Now that I'm retired, I an looking into why people are using things like downloadable fonts more than OS fonts, (amongs other things) when for years we have used fonts that are not only x-os but also cost nothing, both in terms of bandwidth and cost, and especially the 'why' in these days of font-smoothing where unless one uses extremely large sizes, no user will notice any difference.

So why is font Awesome important, especially when the old graphic fonts such as Wingdings, (or the Apple OS equivalent) -

https://www.microsoft.com/typography/fonts/font.aspx?FMID=1698

being used by so many in preference to the windows and Apple OS equivalents?