Some people use monospace fonts with ligatures specific to common programming languages: https://github.com/tonsky/FiraCode is one such example.
(To save people the click: LaTeX ligatures != Fira ligatures. Most Fira ligatures are for programming operators/comparators and they are made to take as much space as the non-ligature version.)
The only difference is that one ligature applies to alphabetic characters and the other to non-alphabetic characters.
Ligatures can be used to make some font aesthetically pleasing like this: http://www.impallari.com/lobster/
Or they can be abused like this: https://pixelambacht.nl/2015/sans-bullshit-sans/
It is perfectly possible for a font to have alphabetic and non-alphabetic ligatures.
It's not a "must have", but I find it more readable and pleasing than using regular fonts.