Earlier quoted context omitted.
A ligature is more functional than not using one. They obscure the code for about 5 seconds the first time you see them, and then never again. After those 5 seconds, you register a new semantic symbol in the brain. It is objectively easier for your brain to parse a single arrow symbol than it is to parse => in a monospace font. For the latter, you are scanning two symbols and only after seeing them both can your brai…
If your programming language wants to use an ⇒ symbol there's a perfectly good codepoint for that already. I don't want complexity to be hiding in my font where I would never even think to look for it. (For example imagine searching the documentation to understand a use of ⇒ and finding it doesn't exist in your programming language)
I wouldn’t know where to get the “⇒” codepoint, and getting is probably more effort than just writing “==>” with the added benefit of my teammates not having to use the ligature (or figure out the symbol) if they don’t want to either.