True, but <> in Perl is called the diamond while, in other languages it means “not equal”. If we take ligatures seriously, we’d need them to be language-aware to select the appropriate concept. And for a font to have to be aware of all languages that can express ideas with it is a violent violation of the separation of concerns principle.

If languages opt to make “≠” equivalent to “!=“, match all styles of open/close quotes, and enable me to attribute a value to a variable using an arrow, that’s great.

In the meantime, I’m not sure they are a net positive in all cases and fear they may drive unfortunate syntax choices for people who design languages.

PureScript and Haskell <> is concat in most Preludes. However, both languages allow you create your own infix operators and you can use Unicode.

>If we take ligatures seriously, we’d need them to be language-aware to select the appropriate concept.

It's possible in Emacs: to enable relevant ligatures for an active mode.